Systems and methods for reducing vehicle valve degradation

ABSTRACT

Methods and systems are provided for reducing degradation and issues related to noise, vibration and harshness (NVH) for a canister purge valve configured to regulate a flow of fuel vapors from a fuel vapor canister to an engine in response to a request to purge the fuel vapor canister of fuel vapors. In one example, a method may include purging the fuel vapor canister by synchronizing a timing of opening and closing events of the canister purge valve to correspond with instances where a pressure difference across the canister purge valve is lower as compared to higher in terms of pressure oscillations across the canister purge valve during the purging. In this way, higher loads and stress on the canister purge valve may be avoided, thus reducing degradation and NVH issues.

FIELD

The present description relates generally to methods and systems forcontrolling one or more valves configured to regulate a flow of fuelvapors in a vehicle fuel system and/or evaporative emissions system, thecontrolling a function of engine operating conditions.

BACKGROUND/SUMMARY

Some automotive fuels may exhibit rapid evaporation in response todiurnal variations in ambient temperature. Emissions resulting from suchvapors may be reduced in automotive applications via evaporativeemission control systems (EVAP), The EVAP systems include a fuel vaporstorage canister containing adsorbent, such as carbon, that traps thosefuel vapors and feeds them back to the vehicle's engine for combustionduring canister purging operations, thus, reducing evaporative emissionsfrom the vehicle and improving fuel economy.

In a canister purge operation, a canister purge valve (CPV) coupledbetween the engine intake and the fuel canister may be duty cycled,allowing for intake manifold vacuum to be applied to the fuel canister.On a boosted engine, that vacuum draw may be supplied via an ejectorduring boosted operation. Simultaneously, a canister vent valve coupledbetween the fuel canister and atmosphere can be opened, allowing forfresh air to enter the canister. Further, in some examples, a fuel tankisolation valve coupled between the fuel tank and the fuel canister maybe closed to reduce the flow of fuel vapors from the fuel tank to theengine. This configuration facilitates desorption of stored fuel vaporsfrom the adsorbent material in the canister, regenerating the adsorbentmaterial for further fuel vapor adsorption.

Canister purge valves in EVAP systems that are duty cycled may havedurability issues. Furthermore, opening and closing the CPV when thereis a high pressure difference across the valve may result in the CPVexperiencing higher loads and stresses as compared to situations wherethere is a lower pressure difference across the valve. Depending on thefrequency and duty cycle of the purge valve opening and closing duringpulsed flow control compared to engine firing frequency, more or lessopenings can occur at varying pressure differences, thus leading tounequal degradation of the valve due to the higher loads and stresses.

The inventors herein have recognized the above-mentioned issues anddesires, and have developed systems and methods to at least partiallyaddress them. In one example, a method comprises purging a fuel vaporcanister that captures and stores fuel vapors from a fuel system of avehicle by synchronizing a timing of opening and closing events of acanister purge valve to correspond with instances where a pressuredifference across the canister purge valve is lower as compared tohigher in terms of pressure oscillations across the canister purge valveduring purging the fuel vapor canister. In this way, issues related todurability of the CPV may be reduced or avoided.

In one example of the method, the method may further comprise adjustingthe timing of the opening and the closing events of the canister purgevalve in response to changes in the pressure oscillations across thecanister purge valve during purging the fuel vapor canister.

As another example of the method, the method may further comprisecontrolling a duty cycle of the canister purge valve while synchronizingthe timing of the opening and the closing events of the canister purgevalve to correspond with the instances where the pressure differenceacross the canister purge valve is lower as compared to higher in termsof the pressure oscillations.

As another example, the pressure oscillations are a function of at leastoperating conditions of an engine that receives purge gasses from thefuel vapor canister. In such an example, the method may includedetermining a frequency, a phase, and an amplitude of the pressureoscillations across the canister purge valve in order to synchronize thetiming of the opening and the closing events of the canister purge valveto correspond with the instances where the pressure difference acrossthe canister purge valve are lower as compared to higher in terms of thepressure oscillations. In such a method, determining the frequency, thephase and the amplitude of the pressure oscillations may include mappingthe pressure oscillations based on one or more of at least an enginespeed, an engine load, a timing of opening and/or closing of intakeand/or exhaust valves of the engine, and an ambient temperature. Inanother example, determining the frequency, the phase and the amplitudeof the pressure oscillations may be based at least in part on feedbackfrom a pressure sensor at the canister purge valve. In yet anotherexample, determining the frequency, the phase, and the amplitude of thepressure oscillations may be based at least in part on a differencebetween an engine intake pressure and a fuel system pressure with thefuel system coupled to atmosphere, corrected for an offset that may bemodelled as a function of a restriction of a buffer section of the fuelvapor canister.

In another example of the method, synchronizing the timing of theopening and the closing events of the canister purge valve to correspondwith the instances where the pressure difference across the canisterpurge valve is lower as compared to higher in terms of the pressureoscillations across the canister purge valve may further comprisecontrolling a pulse width modulation signal to the canister purge valvebased on the pressure oscillations across the canister purge valve.

In still another example of the method, synchronizing the timing of theopening and the closing events of the canister purge valve to correspondwith the instances where the pressure difference across the canisterpurge valve is lower as compared to higher in terms of the pressureoscillations across the canister purge valve improves durability andreduces issues related to noise, vibration and harshness of the canisterpurge valve.

In yet another example of the method, synchronizing the timing of theopening and the closing events of the canister purge valve to correspondwith the instances where the pressure difference across the canisterpurge valve is lower as compared to higher in terms of the pressureoscillations across the canister purge valve further comprisescontrolling the canister purge valve to open and/or close within athreshold time duration in relation to the pressure oscillations acrossthe canister purge valve, the threshold time duration corresponding towhen the pressure difference is lower as compared to higher in terms ofthe pressure oscillations across the canister purge valve.

The above advantages and other advantages, and features of the presentdescription will be readily apparent from the following DetailedDescription when taken alone or in connection with the accompanyingdrawings.

It should be understood that the summary above is provided to introducein simplified form a selection of concepts that are further described inthe detailed description. It is not meant to identify key or essentialfeatures of the claimed subject matter, the scope of which is defineduniquely by the claims that follow the detailed description.Furthermore, the claimed subject matter is not limited toimplementations that solve any disadvantages noted above or in any partof this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic description of an engine including a fuelsystem, and an evaporative emissions system.

FIG. 2 graphically illustrates pressure oscillations across a canisterpurge valve as a function of engine operating conditions.

FIG. 3 depicts a high-level example method for selecting an appropriatestrategy to conduct a canister purging event to reduce wear and tear ona canister purge valve.

FIG. 4 depicts a high-level example method for conducting a canisterpurging operation under conditions of a remote engine start event and/ora deceleration fuel shut-off event.

FIG. 5A depicts an example timeline for ramping up a duty cycle of acanister purge valve during a canister purging event, where a pulsewidth modulation (PWM) signal to the CPV is controlled as a function ofpressure oscillations across the CPV.

FIG. 5B depicts an example timeline illustrating a timing of voltagepulses applied to the CPV, where the CPV comprises a solenoid valve, andwhere a frequency of valve pulsing is equal to or less than a frequencyof pressure oscillations across the CPV.

FIG. 5C depicts an example timeline illustrating a timing of voltagepulses applied to the CPV as in FIG. 5B, where a frequency of valvepulsing is greater than a frequency of pressure oscillations across theCPV.

FIG. 5D depicts an example timeline illustrating a timing of voltagepulses applied to the CPV as in FIGS. 5B-5C, where a frequency of valvepulsing is lower than a frequency of pressure oscillations across theCPV, and where CPV duty cycle changes without a corresponding change infrequency of the valve pulsing.

FIG. 6 depicts an example timeline for conducting canister purgingaccording to the methodology depicted at FIGS. 3-4.

FIG. 7 depicts a high-level example method for conducting a fuel tankdepressurization routine that reduces wear and tear on a fuel tankpressure control valve (TPCV).

FIG. 8 depicts an example timeline for conducting the fuel tankdepressurization routine according to the method depicted at FIG. 7.

FIG. 9 depicts a high-level example method that continues from FIG. 3,and includes conducting a cleaning operation on the CPV during purgingof the canister.

FIG. 10 depicts a high-level example method for determining whether thecleaning routine depicted at FIG. 9 was successful.

FIG. 11 depicts an example timeline for conducting the CPV cleaningoperation according to the method of FIG. 9.

FIG. 12 depicts an example timeline for verifying whether the CPVcleaning routine was successful, according to the method of FIG. 10.

DETAILED DESCRIPTION

The following description relates to systems and methods for reducingdegradation of one or more valves that control flow of fuel vapors in avehicle fuel system and/or evaporative emissions system. In one examplethe valve is a canister purge valve (CPV) positioned in a purge linecoupling a fuel vapor canister to engine intake. In another example thevalve is a fuel tank pressure control valve (TPCV) that is used fordepressurizing the fuel tank under particular vehicle operatingconditions. The systems and methods discussed herein are particularlyapplicable to hybrid electric vehicles, such as the hybrid vehiclesystem of FIG. 1. Specifically, a fuel vapor canister traps and storesfuel vapors from a vehicle fuel system, and at a later time, thecontents of the canister are purged to the engine where the stored fuelvapors are combusted. To purge the canister, the CPV can be pulse widthmodulated (PWM) to open and close at a particular frequency. However,pressure differences across the CPV may affect the forces and stressesfor each opening and closing event of the CPV. As one side of the CPV isconnected to engine intake, pressure oscillations during canisterpurging events stemming from engine operation (e.g. intake and exhaustvalve opening/closing, phasing/timing changes when variable camshafttiming is used to alter intake and/or exhaust valve timing, etc.) mayresult in situations where the CPV is commanded open at times whenpressure across the CPV is greater as compared to lower in terms of thepressure oscillations. This may disproportionately adversely impact CPVfunction (e.g. lead to degradation) as compared to CPV opening/closingevents when pressure across the CPV is lower in terms of the pressureoscillations. Furthermore, when the CPV is opened/closed when pressuredifferences across the CPV are greater (as compared to lower) in termsof the pressure oscillations, issues related to undesirable noise,vibration and harshness (NVH) may be increased. Similar issues may arisein duty cycling the TPCV to relieve pressure. For example, if the TPCVis controlled to open and/or close when pressure differences are high ascompared to low in terms of pressure oscillations across the TPCV duringfuel tank depressurization routines, then TPCV degradation may occur ata faster rate than if the TPCV is controlled to open and/or close whenthe pressure differences are low as compared to high. Thus, it is hereinrecognized that it may be desirable to control the PWM signal to the CPVor TPCV such that opening and closing events of are timed to coincidewith lower pressure differences across the valve in terms of thepressure oscillations. Depicted at FIG. 2 is an example illustration ofsuch pressure oscillations across a CPV during a canister purgingoperation, highlighting points along the pressure oscillation wave wherethe CPV may be opened/closed in order to reduce degradation of the CPVand to reduce NVH issues.

FIG. 3 depicts an example method for selecting whether to timeopening/closing of the CPV with the points of a pressure oscillationwave that comprise the lower pressure differences across the CPV interms of the pressure oscillations as compared to greater pressuredifferences, or to take a different approach. Specifically, there may besome circumstances of vehicle operation where instead of timing the CPVopening/closing events as discussed, it may instead be desirable topurge the canister immediately with a 100% duty cycle, which may greatlyreduce opportunities for degradation of the CPV and which additionallymay aggressively purge the canister which may be desirable for hybridvehicles with limited engine run time. Such circumstances include remoteengine start events and deceleration fuel shut off (DFSO) events, and itwill be discussed in further detail below as to why such conditions maybe amenable to aggressively purging the canister with a 100% duty cycle.Thus, if it is determined that the vehicle is in the process of a remotestart event or a DFSO mode, then the method of FIG. 4 may be used topurge the canister.

FIG. 5A depicts an example timeline illustrating how, depending on thepressure oscillations across the CPV, a purge ramp may be conducted. Inother words, FIG. 5A depicts how duty cycle and frequency ofopening/closing events of the CPV may be adjusted or controlled in orderto increase an amount of vapors purged to the engine intake during apurge event, while maintaining the CPV opening/closing events tocoincide with low pressure events in terms of the pressure oscillations.The CPV may be a solenoid-actuated valve, and accordingly, FIG. 5Bdepicts how voltage pulses to the CPV may be controlled in order to timeCPV opening/closing events with low pressure points in terms of thepressure oscillations across the CPV during a purging event. In someexamples, the frequency of CPV pulsing may be greater than a frequencyof pressure oscillations across the CPV, as depicted at FIG. 5C.Alternatively, another example includes a situation where the frequencyof CPV pulsing may be less than the frequency of pressure pulsationsacross the CPV, as depicted at FIG. 5D. An example timeline forconducting a canister purging operation according to the methods ofFIGS. 3-4, is depicted at FIG. 6.

As discussed above, in other examples it may be desirable to control aTPCV in similar fashion as that discussed in terms of the CPV, to reducevalve degradation during fuel tank depressurization events. A method fordoing so is depicted at FIG. 7. FIG. 8 depicts an example timeline forconducting a fuel tank depressurization, where the TPCV is timed to openand close at times corresponding to low pressure differences across theTPCV in terms of pressure oscillations across the TPCV, according to themethod of FIG. 7.

While controlling CPV opening and closing events to coincide with lowpressure differences across the CPV during purging of the canister mayreduce degradation, there may be circumstances where the CPV isdetermined to be not sealing properly when closed. In such a case, itmay be desirable to time CPV opening and closing events to coincide withhigh pressure differences across the CPV in terms of pressureoscillations during purging the canister. In this way, whatever iscausing the CPV to not seal properly when closed (e.g. carbon pellets,dust, fibers, cardboard, etc.), may be dislodged, resulting in the CPVonce again sealing properly. Accordingly, a method for conducting a CPVcleaning operation is depicted at FIG. 9. After conducting the CPVcleaning operation, the method of FIG. 10 may be used to ascertainwhether the CPV cleaning routine successfully restored the ability ofthe CPV to seal properly or as expected, when commanded closed. Atimeline for conducting the CPV cleaning operation according to themethod of FIG. 9, is depicted at FIG. 11. A timeline for ascertainingwhether such a CPV cleaning operation resulted in the ability of the CPVto seal properly according to the method of FIG. 10, is depicted at FIG.12.

Turning now to FIG. 1, a schematic depiction of a hybrid vehicle system6 is presented that can derive propulsion power from engine system 10and/or an on-board energy storage device, such as a battery system (seebelow). An energy conversion device, such as a generator (see below),may be operated to absorb energy from vehicle motion and/or engineoperation, and then convert the absorbed energy to an energy formsuitable for storage by the energy storage device. Engine system 10 maycomprise a multi-cylinder internal combustion engine, which may beincluded in a propulsion system of an automotive vehicle. Engine 10 maybe controlled at least partially by a control system includingcontroller 12 and by input from a vehicle operator 130 via an inputdevice 132. In this example, input device 132 includes an acceleratorpedal and a pedal position sensor 134 for generating a proportionalpedal position signal PP.

Engine 10 may include a lower portion of the engine block, indicatedgenerally at 26, which may include a crankcase 28 encasing a crankshaft30 with oil well 32 positioned below the crankshaft. An oil fill port 29may be disposed in crankcase 28 so that oil may be supplied to oil well32. Oil fill port 29 may include an oil cap 33 to seal oil fill port 29when the engine is in operation. A dip stick tube 37 may also bedisposed in crankcase 28 and may include a dipstick 35 for measuring alevel of oil in oil well 32. An oil temperature sensor 51 may beincluded in crankcase 28, and may monitor temperature of oil in oil well32. In addition, crankcase 28 may include a plurality of other orificesfor servicing components in crankcase 28. These orifices in crankcase 28may be maintained closed during engine operation so that a crankcaseventilation system (described below) may operate during engineoperation.

The upper portion of engine block 26 may include a combustion chamber(i.e., cylinder) 34. The combustion chamber 34 may include combustionchamber walls 36 with piston 38 positioned therein. Piston 38 may becoupled to crankshaft 30 so that reciprocating motion of the piston istranslated into rotational motion of the crankshaft. Combustion chamber34 may receive fuel from fuel injector 45 (configured herein as a directfuel injector) and intake air from intake manifold 44 which ispositioned downstream of throttle 42. The engine block 26 may alsoinclude an engine coolant temperature (ECT) sensor 46 input into anengine controller 12.

In some embodiments, each cylinder of engine 10 may include a spark plug53 for initiating combustion. An ignition system (not shown) may providean ignition spark to cylinder 34 via spark plug 53 in response to aspark advance signal from a controller, under select operating modes.

Throttle 42 may be disposed in the engine intake to control the airflowentering intake manifold 44 and may be preceded upstream by compressor50 followed by charge air cooler 52, for example. Throttle 42 maycomprise an electrically actuated throttle, for example. An air filter54 may be positioned upstream of compressor 50 and may filter fresh airentering intake passage 13. The intake air may enter combustion chamber34 via intake valve system 40. Likewise, combusted exhaust gas may exitcombustion chamber 34 via exhaust valve system 41. In one example, oneor more of the intake valve system and the exhaust valve system may becam-actuated. In another example, one or more of the intake valve systemand the exhaust valve system may be electrically-actuated. Intake airmay bypass compressor 50 via compressor bypass conduit 56, duringconditions wherein compressor bypass valve (CBV) 55 is opened. In thisway, pressure buildup at the compressor inlet may be relieved.

Each cylinder of engine 10 may include one or more intake valves and oneor more exhaust valves. For example, cylinder 34 is shown including atleast one intake valve 94 and at least one exhaust valve 95 located atan upper region of cylinder 34.

Intake valve 94 may be controlled by a controller via actuator 83.Similarly, exhaust valve 95 may be controlled by a controller viaactuator 84. During some conditions, the controller may vary the signalsprovided to actuators 83 and 84 to control the opening and closing ofthe respective intake and exhaust valves. The position of intake valve94 and exhaust valve 95 may be determined by respective position sensors98 and 99, respectively. The valve actuators may be of the electricvalve actuation type or cam actuation type, or a combination thereof.The intake and exhaust valve timing may be controlled concurrently orany of a possibility of variable intake cam timing, variable exhaust camtiming, twin independent variable cam timing (TiVCT), or fixed camtiming may be used. Each cam actuation system may include one or morecams (e.g. actuator 83 and/or 84) and may utilize one or more of camprofile switching (CPS), variable cam timing (VCT), variable valvetiming (VVT) and/or variable valve lift (VVL) systems that may beoperated by a controller to vary valve operation. For example, cylinder34 may alternatively include an intake valve controlled via electricvalve actuation and an exhaust valve controlled via cam actuationincluding CPS and/or VCT. In other embodiments, the intake and exhaustvalves may be controlled by a common valve actuator or actuation system,or a variable valve timing actuator or actuation system.

Shown for illustrative purposes at FIG. 1 is an example of TiVCT.Specifically, an intake camshaft 181 and an exhaust camshaft 182 areillustrated. It may be understood that such a configuration may enablethe ability to advance or retard timing of both the intake camshaft 181and the exhaust camshaft 182 independently. Such an ability may allowfor improved power and torque, particularly at lower engine speed(engine RPM), as well as improved fuel economy and reduced emissions.Such an ability may further enable precise control over intake andexhaust valve position, which may include in some examples positioning aparticular cylinder with intake and exhaust valves both at leastpartially open.

In an example, a first oil pressure-controlled actuator 183 undercontrol of the controller may regulate rotation of intake camshaft 181,and a second oil pressure-controlled actuator 184 may regulate rotationof second camshaft 182. In this way the first and second oilpressure-controlled actuators may control the camshafts to advance orretard engine timing based on operating conditions. For example, thecontroller may utilize crankshaft position sensor 197 and positionsensor(s) 98 and 99 to determine engine timing.

While the example depicted herein at FIG. 1 illustrates the actuators(e.g. 183 and 184) of the camshafts as oil pressure-controlled, theremay be some examples where instead of oil pressure driven cam phasing,cam torque actuation (CTA) may be employed, which may utilize existingtorsional energy in the valve train to rotate the camshaft(s), as iscommonly understood in the art.

Furthermore, it may be understood that in examples where the vehicleincludes TiVCT, an EGR valve (e.g. 164) and EGR passage (e.g. 162 a, 162b) may not be included in the vehicle system, as retarding exhaust camtiming may achieve a similar result as recirculating exhaust gases.

In some examples, a first intake air oxygen sensor 43 a (first IAO2sensor) may be positioned downstream of throttle 42. Furthermore, insome examples, an air intake system hydrocarbon (AIS HC) trap 47 may bepositioned downstream of air filter 54, but upstream of compressor 50.Still further, in some examples, a second intake air oxygen sensor 43 b(second IAO2 sensor) may be positioned upstream of the throttle 42.Second intake air oxygen sensor 43 b may constitute an intake air oxygensensor utilize for exhaust gas recirculation (EGR) purposes, forexample, and may be used in vehicles in which fuel is injected directly,for example gasoline turbo direct injection (GTDI) engines.

Exhaust combustion gases exit the combustion chamber 34 via exhaustpassage 60 located upstream of turbine 62. An exhaust gas sensor 64 maybe disposed along exhaust passage 60 upstream of turbine 62. Turbine 62may be equipped with a wastegate (not shown) bypassing it. Exhaust gassensor 64 may be a suitable sensor for providing an indication ofexhaust gas air/fuel ratio such as a linear oxygen sensor or UEGO(universal or wide-range exhaust gas oxygen), a two-state oxygen sensoror EGO, a HEGO (heated EGO), a NOx, HC, or CO sensor. Exhaust gas sensor64 may be connected with controller 12. Engine exhaust 60 may furtherinclude one or more emission control devices 63 mounted in aclose-coupled position. The one or more emission control devices mayinclude a three-way catalyst, lean NOx trap, diesel particulate filter,oxidation catalyst, etc. In some examples, multiple exhaust gas sensorsmay be positioned both upstream and downstream of emission controldevice 63. In some examples, an electric heater 119 may be coupled tothe emission control device(s), and may be under control of thecontroller. Such an electric heater may be utilized in some examples toraise temperature of the emission control device to a light-offtemperature, or otherwise referred to as operating temperature.

In the example of FIG. 1, a positive crankcase ventilation (PCV) system16 is coupled to the engine intake so that gases in the crankcase may bevented in a controlled manner from the crankcase. During non-boostedconditions (when manifold pressure (MAP) is less than barometricpressure (BP)), the crankcase ventilation system 16 draws air intocrankcase 28 via a breather or crankcase ventilation tube 74. A firstside 101 of crankcase ventilation tube 74 may be mechanically coupled,or connected, to fresh air intake passage 13 upstream of compressor 50.In some examples, the first side 101 of crankcase ventilation tube 74may be coupled to intake passage 13 downstream of air filter 54 (asshown). In other examples, the crankcase ventilation tube may be coupledto intake passage 13 upstream of air filter 54. A second, opposite side102 of crankcase ventilation tube 74 may be mechanically coupled, orconnected, to crankcase 28 via an oil separator 81.

Crankcase ventilation tube 74 further includes a sensor 77 coupledtherein for providing an estimate about air flowing through crankcaseventilation tube 74 (e.g., flow rate, pressure, etc.). In someembodiments, crankcase vent tube sensor 77 may be a pressure sensor,referred to herein as a crankcase pressure sensor (CKCP sensor) 77. Whenconfigured as a pressure sensor, CKCP sensor 77 may be an absolutepressure sensor or a gauge sensor. In an alternate embodiment, sensor 77may be a flow sensor or flow meter. In still another embodiment, sensor77 may be configured as a venturi. In some embodiments, in addition to apressure or flow sensor 77, the crankcase vent tube may optionallyinclude a venturi 75 for sensing flow there-through. In still otherembodiments, pressure sensor 77 may be coupled to a neck of venturi 75to estimate a pressure drop across the venturi. One or more additionalpressure and/or flow sensors may be coupled to the crankcase ventilationsystem at alternate locations. For example, a barometric pressure sensor(BP sensor) 57 may be coupled to intake passage 13, upstream of airfilter 54, for providing an estimate of barometric pressure. In oneexample, where crankcase vent tube sensor 77 is configured as a gaugesensor, BP sensor 57 may be used in conjunction with gauge pressuresensor 77. In some embodiments, pressure sensor 61 may be coupled inintake passage 13 downstream of air filter 54 and upstream of compressor50 to provide an estimate of the compressor inlet pressure (CIP).However, since crankcase vent tube pressure sensor 77 may provide anaccurate estimate of a compressor inlet pressure during elevated engineair flow conditions (such as during engine run-up), the need for adedicated CIP sensor may be reduced. Further still, a pressure sensor 59may be coupled downstream of compressor 50 for providing an estimate ofa throttle inlet pressure (TIP). Any of the above-mentioned pressuresensors may be absolute pressure sensor or gauge sensors.

PCV system 16 also vents gases out of the crankcase and into intakemanifold 44 via a conduit 76 (herein also referred to as PCV line 76).In some examples, PCV line 76 may include a PCV valve 78, which may bean electronically controlled valve that is controlled by controller 12.In another example, the PCV valve 78 may comprise a passively-actuatablemechanical valve. For example, the PCV valve may actively or passivelyvary its flow restriction in response to the pressure drop across it (orflow rate through it). Thus, in one example PCV valve 78 may be anelectronically controlled valve wherein controller 12 may command asignal to change a position of the valve from a fully open position (ora position of high flow) to a fully closed position (or a position of noflow), or vice versa, or any position there-between. In another example,the PCV valve 78 may be passively actuated.

The gases (referred to herein as blow-by gasses) in crankcase 28 mayconsist of un-burned fuel or un-combusted fuel, un-combusted fuel vapor,un-combusted air, and fully or partially combusted gases. Further, oilmist or vapor may also be present. As such, various oil separators maybe incorporated in crankcase ventilation system 16 to reduce exiting ofthe oil mist from the crankcase through the PCV system. For example, PCVline 76 may include a uni-directional oil separator 80 which filters oilfrom vapors exiting crankcase 28 before they re-enter the intakemanifold 44. Another oil separator 81 may be disposed in crankcaseventilation tube 74 to remove oil from the stream of gases exiting thecrankcases during boosted operation. Additionally, PCV line 76 may alsoinclude a vacuum sensor 82 coupled to the PCV system. In otherembodiments, a MAP sensor 39 or manifold vacuum (ManVac) sensor may belocated in intake manifold 44.

Engine system 10 is coupled to a fuel system 18. Fuel system 18 includesa fuel tank 20 coupled to a fuel pump 21 and a fuel vapor canister 90.During a fuel tank refueling event, fuel may be pumped into the vehiclefrom an external source through refueling port 25. Fuel tank 20 may holda plurality of fuel blends, including fuel with a range of alcoholconcentrations, such as various gasoline-ethanol blends, including E10,E85, gasoline, etc., and combinations thereof. A fuel level sensor 22located in fuel tank 20 may provide an indication of the fuel level(“Fuel Level Input”) to controller 12. As depicted, fuel level sensor 22may comprise a float connected to a variable resistor. Alternatively,other types of fuel level sensors may be used.

Fuel pump 21 is configured to pressurize fuel delivered to the injectorsof engine 10, such as example injector 45. It will be appreciated thatfuel system 18 may be a return-less fuel system, a return fuel system,or various other types of fuel system. Vapors generated in fuel tank 20may be routed to fuel vapor storage canister 90 (also referred to hereinas fuel vapor canister, or just canister), via conduit 93, before beingpurged to engine intake manifold 44.

Fuel vapor canister 90 may be positioned in evaporative emissions system19. Fuel vapor canister 90 is filled with an appropriate adsorbent fortemporarily trapping fuel vapors (including vaporized hydrocarbons)generated during fuel tank refueling operations. In one example, theadsorbent used is activated charcoal. When purging conditions are met,such as when the canister is saturated, vapors stored in fuel vaporcanister 90 may be purged to engine intake passage 13 by openingcanister purge valve (CPV) 92. While a single canister 90 is shown, itwill be appreciated that evaporative emissions system 19 may include anynumber of canisters. In one example, CPV 92 may be a solenoid valvewherein opening or closing of the valve is performed via actuation of acanister purge valve solenoid.

In some examples, a purge line pressure sensor 67 may be positioned inpurge line 91. By incorporating pressure sensor 67, the CPV may becontrolled to be opened/closed when pressure across the CPV is low ascompared to high during a canister purging event, as will be discussedin detail below. However, such control of the CPV may be possible in theabsence of such a purge line pressure sensor 67, without departing fromthe scope of this disclosure.

Canister 90 may include a buffer (or buffer region) 90 a and a mainregion 90 b, each of the main region 90 b and the buffer 90 a comprisingadsorbent. The volume of the buffer may be smaller than (e.g., afraction of) the volume of the main region 90 b. Adsorbent in the buffermay be same as, or different from, the adsorbent in the main region(e.g., both may include charcoal). The buffer may be positioned withincanister 90 such that during canister loading, fuel tank vapors arefirst adsorbed within the buffer, and then when the buffer is saturated,further fuel tank vapors are adsorbed in the main region 90 b of thecanister 90. In comparison, during canister purging, fuel vapors arefirst desorbed from the canister (e.g., to a threshold amount) beforebeing desorbed from the buffer. In other words, loading and unloading ofthe buffer is not linear with the loading and unloading of the canister.As such, the effect of the canister buffer is to dampen any fuel vaporspikes flowing from the fuel tank to the canister, thereby reducing thepossibility of any fuel vapor spikes going to the engine.

Canister 90 includes a vent line 86 for routing gases out of thecanister 90 to the atmosphere when storing, or trapping, fuel vaporsfrom fuel tank 20. Vent line 86 may also allow fresh air to be drawninto fuel vapor canister 90 when purging stored fuel vapors to engineintake passage 13 via purge line 91 and CPV 92. While this example showsvent 86 communicating with fresh, unheated air, various modificationsmay also be used. Vent 86 may include a canister vent valve (CVV) 87 toadjust a flow of air and vapors between canister 90 and the atmosphere.The canister vent valve may also be used for diagnostic routines. Whenincluded, the vent valve may be opened during fuel vapor storingoperations (for example, during fuel tank refueling) so that air,stripped of fuel vapor after having passed through the canister, can bepushed out to the atmosphere. Likewise, during purging operations (forexample, during canister regeneration and while the engine is running),the vent valve may be opened to allow a flow of fresh air to strip thefuel vapors stored in the canister. In one example, canister vent valve87 may be a solenoid valve wherein opening or closing of the valve isperformed via actuation of a canister vent solenoid. In particular, thecanister vent valve may be a default-open valve that is closed uponactuation of the canister vent solenoid. In some examples, an air filter(not shown) may be coupled in vent 86 between canister vent valve 87 andatmosphere.

Hybrid vehicle system 6 may have reduced engine operation times due tothe vehicle being powered by engine system 10 during some conditions,and by the energy storage device under other conditions. While thereduced engine operation times reduce overall carbon emissions from thevehicle, they may also lead to insufficient purging of fuel vapors fromthe vehicle's emission control system. To address this, a fuel tankisolation valve 85 may be included in conduit 93 such that fuel tank 20is coupled to canister 90 via the valve. During regular engineoperation, isolation valve 85 may be kept closed to limit the amount ofdiurnal or “running loss” vapors directed to canister 90 from fuel tank20. During refueling operations, and selected purging conditions,isolation valve 85 may be temporarily opened, e.g., for a duration, todirect fuel vapors from the fuel tank 20 to canister 90. While thedepicted example shows isolation valve 85 positioned along conduit 93,in alternate embodiments, the isolation valve may be mounted on fueltank 20. The fuel system may be considered to be sealed when isolationvalve 85 is closed.

One or more pressure sensors 23 may be coupled to fuel system 18 forproviding an estimate of a fuel system pressure. In one example, thefuel system pressure is a fuel tank pressure, wherein pressure sensor 23is a fuel tank pressure sensor (fuel tank pressure transducer, or FTPT)coupled to fuel tank 20 for estimating a fuel tank pressure or vacuumlevel. While the depicted example shows pressure sensor 23 directlycoupled to fuel tank 20, in alternate embodiments, the pressure sensormay be coupled between the fuel tank and canister 90, specificallybetween the fuel tank and isolation valve 85. In some examples, anotherpressure sensor 126 may be positioned in conduit 93 between the FTIV andcanister 90.

One or more temperature sensors 24 may also be coupled to fuel system 18for providing an estimate of a fuel system temperature. In one example,the fuel system temperature is a fuel tank temperature, whereintemperature sensor 24 is a fuel tank temperature sensor coupled to fueltank 20 for estimating a fuel tank temperature. While the depictedexample shows temperature sensor 24 directly coupled to fuel tank 20, inalternate embodiments, the temperature sensor may be coupled between thefuel tank and FTIV 85. A canister temperature sensor 97 may be coupledto canister 90 and configured to indicate temperature changes of theadsorbent material within the canister. As fuel vapor adsorption is anexothermic reaction and fuel vapor desorption is an endothermicreaction, the canister temperature may be used to indicate a quantity offuel vapor adsorbed during a venting event, and/or the quantity of fuelvapor desorbed during a purging operation.

In some examples, a fuel tank pressure control valve 125 (TPCV) may bepositioned in a conduit 124 that stems from conduit 93. TPCV 125 may insome examples be duty cycled to relieve pressure in fuel tank 20. Aquantity and rate of vapors released by the TPCV may be determined bythe duty cycle of an associated TPCV solenoid (not shown). Fuel vaporsreleased from the fuel tank may be drawn into the engine for combustion,as will be elaborated in further detail below. The duty cycle of theTPCV may be determined by the vehicle's powertrain control module (PCM),such as controller 12, responsive to engine operating conditions such asengine speed-load conditions, an air-fuel ratio, etc. As mentioned aboveand which will be elaborated further below (see FIG. 7, for example),duty cycling the TPCV may lead to degradation over time, if mitigatingaction is not taken to reduce the potential for such degradation. It maybe understood that, when cycling of the TCPV is conducted, the fuel tankisolation valve 85 may be maintained closed.

Fuel vapors released from canister 90, for example during a purgingoperation, may be directed into engine intake manifold 44 via purge line91. The flow of vapors along purge line 91 may be regulated by CPV 92,coupled between the fuel vapor canister and the engine intake. Thequantity and rate of vapors released by the CPV may be determined by theduty cycle of an associated canister purge valve solenoid (not shown).As such, the duty cycle of the canister purge valve solenoid may bedetermined by the vehicle's powertrain control module (PCM), such ascontroller 12, responsive to engine operating conditions, including, forexample, engine speed-load conditions, an air-fuel ratio, a canisterload, etc. However, as discussed above and which will be discussed inmore depth below, duty cycling the CPV may lead to degradation overtime, where such degradation may be exacerbated or sped up if the CPV isregularly opened when there is high pressure differences across thevalve. In other words, higher pressure differences across the CPV whenthe CPV is commanded open/closed may result in the CPV experiencinghigher loads and stresses as compared to situations where there is alower pressure difference across the valve. Accordingly, discussedherein at the methods depicted at FIGS. 3-4 are control strategies forreducing a frequency at which the CPV is opened when pressure across theCPV is greatest in terms of pressure oscillations across the CPV duringcanister purging events.

Fuel system 18 may be operated by controller 12 in a plurality of modesby selective adjustment of the various valves and solenoids. Forexample, the fuel system may be operated in a fuel vapor storage mode(e.g., during a fuel tank refueling operation and with the engine notrunning), wherein the controller 12 may open isolation valve 85 and CVV87 while closing CPV 92 to direct refueling vapors into canister 90while preventing fuel vapors from being directed into the intakemanifold.

As another example, the fuel system may be operated in a refueling mode(e.g., when fuel tank refueling is requested by a vehicle operator),wherein the controller 12 may open isolation valve 85 and CVV 87, whilemaintaining CPV 92 closed, to depressurize the fuel tank before allowingfuel to be added therein. As such, isolation valve 85 may be kept openduring the refueling operation to allow refueling vapors to be stored inthe canister. After refueling is completed, the isolation valve may beclosed.

As discussed, the fuel system may be operated in a canister purging mode(e.g., after an emission control device light-off temperature has beenattained and with the engine running), wherein the controller 12 mayopen canister purge valve 92 and canister vent valve while closingisolation valve 85. Herein, the vacuum generated by the intake manifoldof the operating engine may be used to draw fresh air through vent 86and through fuel vapor canister 90 to purge the stored fuel vapors intointake manifold 44. In this mode, the purged fuel vapors from thecanister are combusted in the engine. The purging may be continued untilthe stored fuel vapor amount in the canister is below a thresholdcanister load (e.g. less than 5% full of vapors). During purging, alearned vapor amount/concentration can be used to determine the amountof fuel vapors stored in the canister, and then during a later portionof the purging operation (when the canister is sufficiently purged orempty), the learned vapor amount/concentration can be used to estimate aloading state of the fuel vapor canister. Such a vaporamount/concentration may be learned via the output of the exhaust gassensor 64, for example.

Controller 12 is shown in FIG. 1 as a microcomputer, includingmicroprocessor unit 108, input/output ports 110, an electronic storagemedium for executable programs and calibration values shown as read onlymemory chip 112 in this particular example, random access memory 114,keep alive memory 116, and a data bus. Controller 12 may receive varioussignals from sensors 117 coupled to engine 10, including measurement ofinducted mass air flow (MAF) from mass air flow sensor 58; enginecoolant temperature (ECT) from temperature sensor 46; PCV pressure fromvacuum sensor 82; exhaust gas air/fuel ratio from exhaust gas sensor 64;exhaust temperature sensor 65; crankcase vent tube pressure sensor 77,BP sensor 57, CIP sensor 61, TIP sensor 59, canister temperature sensor97, purge line pressure sensor 67, ambient air temperature sensor 107,intake temperature sensor 109, etc. Furthermore, controller 12 maymonitor and adjust the position of various actuators 118 based on inputreceived from the various sensors. These actuators may include, forexample, throttle 42, intake and exhaust valve systems 40, 41, PCV valve78, CPV 92, FTIV 85, CVV 87, TPCV 125, etc. Storage medium read-onlymemory 112 can be programmed with computer readable data representinginstructions executable by processor 108 for performing the methodsdescribed below, as well as other variants that are anticipated but notspecifically listed.

As discussed, hybrid vehicle system 6 may include multiple sources oftorque available to one or more vehicle wheels 171, however, in otherexamples, the vehicle may include an engine without other sources oftorque available. In the example shown, hybrid vehicle system 6 includesan electric machine 152. Electric machine 152 may be a motor or amotor/generator. Crankshaft 30 of engine 10 and electric machine 152 areconnected via a transmission 154 to vehicle wheels 171 when one or moreclutches 172 are engaged. In the depicted example, a first clutch isprovided between crankshaft 30 and electric machine 152, and a secondclutch is provided between electric machine 152 and transmission 154.Controller 12 may send a signal to an actuator of each clutch 172 toengage or disengage the clutch, so as to connect or disconnectcrankshaft from electric machine 152 and the components connectedthereto, and/or connect or disconnect electric machine 152 fromtransmission 154 and the components connected thereto. Transmission 154may be a gearbox, a planetary gear system, or another type oftransmission. The powertrain may be configured in various mannersincluding as a parallel, a series, or a series-parallel hybrid vehicle.

Electric machine 152 receives electrical power from a traction battery158 (also described herein as onboard energy storage device, energystorage device, or battery) to provide torque to vehicle wheels 171.Electric machine 152 may also be operated as a generator to provideelectrical power to charge traction battery 158, for example during abraking operation.

Onboard energy storage device 158 may periodically receive electricalenergy from a power source 191 residing external to the vehicle (e.g.,not part of the vehicle) as indicated by arrow 192. As a non-limitingexample, hybrid vehicle system 6 may be configured as a PHEV, wherebyelectrical energy may be supplied to energy storage device 158 frompower source 191 via an electrical energy transmission cable 193. Duringa recharging operation of energy storage device 158 from power source191, electrical transmission cable 193 may electrically couple energystorage device 158 and power source 191. While the vehicle propulsionsystem is operated to propel the vehicle, electrical transmission cable193 may disconnected between power source 191 and energy storage device158. Controller 12 may identify and/or control the amount of electricalenergy stored at the energy storage device, which may be referred to asthe state of charge (SOC).

In other examples, electrical transmission cable 193 may be omitted,where electrical energy may be received wirelessly at energy storagedevice 158 from power source 191. For example, energy storage device 158may receive electrical energy from power source 191 via one or more ofelectromagnetic induction, radio waves, and electromagnetic resonance.As such, it may be appreciated that any suitable approach may be usedfor recharging energy storage device 158 from a power source that doesnot comprise part of the vehicle.

Hybrid vehicle system 6 may include an exhaust gas recirculation (EGR)system. Specifically, the EGR system may include one or more of highpressure EGR, or low pressure EGR. In the example illustration depictedat FIG. 1, a low pressure EGR system is illustrated. Specifically, anEGR passage is indicated, the EGR passage comprising passage 162 a and162 b. It may be understood that passage 162 a and 162 b may comprisethe same EGR passage, but is indicated as a broken passage for clarity.The EGR passage comprising passage 162 a and 162 b may further includeEGR valve 164. By controlling timing of opening and closing of EGR valve164, an amount of exhaust gas recirculation may be appropriatelyregulated.

In some examples controller 12 may be in communication with a remoteengine start receiver 195 (or transceiver) that receives wirelesssignals 106 from a key fob 104 having a remote start button 105. Inother examples (not shown), a remote engine start may be initiated via acellular telephone, or smartphone based system where a user's cellulartelephone sends data to a server and the server communicates with thevehicle to start the engine.

Furthermore, controller 12 may be in communication with one or moresensors dedicated to indicating the occupancy-state of the vehicle, forexample seat load cells 121, door sensing technology 122, and/or onboardcameras 123.

Thus, discussed herein, a system for a hybrid vehicle may comprise acanister purge valve positioned in a purge line fluidically coupling afuel vapor canister to an intake of an engine. Such a system may furthercomprise a controller with computer readable instructions stored onnon-transitory memory that when executed, cause the controller toreceive a request to purge the fuel vapor canister of fuel vapors to theengine. The controller may store further instructions to, in a firstcondition, control the canister purge valve in a first mode tosynchronize a timing of opening and closing of the canister purge valveas a function of pressure oscillations across the canister purge valve.The controller may store further instructions to, in a second condition,control the canister purge valve in a second mode that includescommanding the canister purge valve fully open without first commandinglower percentage duty cycles in response to the request for purging thefuel vapor canister.

In such a system, the system may further comprise an exhaust catalystpositioned in an exhaust of the engine. In such an example, thecontroller may store further instructions to control the canister purgevalve in the first mode or the second mode provided that a temperatureof the exhaust catalyst is at or above a threshold temperature.

In such a system, the system may further comprise one or more of seatload cells, door sensing technology and/or onboard cameras forindicating occupancy of the hybrid vehicle, and fuel injectors forfueling the engine. In such an example, the controller may store furtherinstructions to control the canister purge valve in the second mode inresponse to an indication of a remote start of the engine where thehybrid vehicle is further indicated to be unoccupied, or in response toan indication of a deceleration fuel shut off event where fuel to theengine is discontinued while engine intake and engine exhaust valvescontinue to operate.

In such a system, the system may further comprise a crankshaft positionsensor, a mass air flow sensor positioned in the intake of the engine, athrottle positioned in the intake of the engine, an ambient airtemperature sensor, position sensors for engine intake and exhaustvalves, an intake temperature sensor, a manifold air pressure sensorpositioned in the intake, and a fuel tank temperature sensor positionedin a fuel system. In such a system, the controller may store furtherinstructions to map a frequency, a phase and an amplitude of thepressure oscillations across the canister purge valve based on dataretrieved from a plurality of two or more of the crankshaft positionsensor, the mass air flow sensor, the ambient air temperature sensor,the position sensors for the engine intake and exhaust valves, theintake temperature sensor, the manifold air pressure sensor and/or thefuel tank temperature sensor. In such an example, controlling thecanister purge valve in the first mode to synchronize the timing ofopening and closing of the canister purge valve as a function ofpressure oscillations across the canister purge valve includescontrolling a pulse width modulation signal to the canister purge valveas a function of the frequency, the phase and the amplitude of thepressure oscillations, such that opening and closing events of thecanister purge valve occur at times in terms of the pressureoscillations where a pressure difference across the canister purge valveis less than a threshold pressure difference, where the thresholdpressure difference is set as a function of the frequency, the phase andthe amplitude of the pressure oscillations.

Turning now to FIG. 2, a graphical illustration 200 depicting pressureoscillations across a CPV is shown. Time is depicted on the x axis, andpressure across the CPV is depicted on the y axis. Thus, line 202depicts pressure across the CPV as a function of time. As depicted,there is a vacuum across the CPV, on top of which there are smallerpressure oscillations. The vacuum stems from the intake manifold (e.g.44) of the engine (e.g. 10). In other words, in this exampleillustration 200, it may be understood that the engine is rotating, andthe opening and closing of intake and exhaust valves (in conjunctionwith throttle position) generates a vacuum in the intake manifold thatis communicated to the CPV.

The pressure oscillations are based on (and vary based on) severalfactors. One such factor is engine firing frequency, which changes withengine speed (RPM). Another such factor is phasing/timing changes ofpressure oscillations when variable camshaft timing (VCT) is used.Another such factor includes how the engine and evaporative emissionssystem is structured, for example length of purge line coupling engineintake to the CPV, etc., and how such structure may contribute tostanding pressure waves. Still another such factor includes temperatureof gas in the intake and purge line, as temperature of gas affects thespeed of sound and thus the propagation of pressure waves. In otherwords, amplitude, frequency, and phasing of pressure oscillations acrossthe CPV change as a function of engine speed, engine load, cam timing,ambient temperature, engine and evaporative emissions system structure,etc.

As discussed above, canister purging operations are conducted by dutycycling the CPV coupled in the purge line between engine intake and thefuel vapor storage canister with the CVV open. In this way, intakemanifold vacuum may be applied to the canister, where fresh air is drawnthrough the canister via the open CVV. The fresh air serves to desorbstored fuel vapors from the canister, which are then routed to engineintake. If the duty cycle of the CPV is pulse width modulated (PWM) at aconstant frequency (e.g. 20 Hz) and the pressure oscillations are notaccounted for in terms of the phasing, frequency and amplitude of thepressure oscillations across the CPV, then the CPV may open and close atrandom points on the pressure wave, as illustrated by filled circles210. While not all CPV opening/closing events in such a scenario mayoccur when pressure across the CPV is greatest, some percentage (see 210a, 210 b, and 210 c) will, and opening/closing the CPV under suchconditions may disproportionately adversely impact CPV durability aswell as contribute to NVH issues.

Alternatively, by synchronizing the PWM signal to the CPV with thefrequency and phasing of the pressure oscillations, the CPV may bephased to open and close when pressure across the CPV is low in terms ofthe pressure oscillations, illustrated by the open circles 205. In thisway, CPV degradation may be reduced over time, and as a result, engineoperation may be improved and undesired evaporative emissions (which mayoccur in certain cases where the CPV becomes degraded) may be reduced.Furthermore, NVH issues may additionally be reduced or avoided.

While illustration 200 depicts a situation where smaller pressureoscillations are on top of a larger vacuum, the systems and methodsdiscussed herein are not limited to such an event. It may be understoodinstead that the systems and methods discussed herein in a broad senserefer to timing opening and closing events of the CPV (and in othercases the TPCV, which will be discussed in further detail below) tocoincide with times when pressure differences across the CPV (or TPCV)are low as compared to high in terms of pressure oscillations across theparticular valve.

Accordingly, inset 250 represents the concept in a different way, toillustrate pressure 252 across the CPV increasing (+) or decreasing (−),over time. Depicted as open circles 255, are times when the CPV may beopened or closed to coincide with low pressure differences across theCPV as compared to high pressure differences. As will be discussed inmore detail below, there may be a threshold pressure difference 256,where above the threshold pressure difference comprises the highpressure difference 260, and where below the threshold pressuredifference comprises the low pressure difference 261. As one example,the threshold pressure difference may be set after determining anamplitude, phase and frequency of the pressure oscillations, and mayinclude setting the threshold pressure difference based on inflectionpoints (depicted as arrows 257) of the pressure oscillation wave. It maybe understood that setting the threshold pressure difference may not belimited to only relying upon inflexion points, but may be set to belower than the inflexion points (thus reducing an amount of time wherethe CPV may be timed to open and close while coinciding with the lowpressure differences). It may be understood that in setting thethreshold pressure difference, a time duration (indicated by dashedlines 258 may additionally be set corresponding to when the CPV may beopened and/or closed to coincide with the low pressure differences ascompared to high pressure differences. Said another way, above thethreshold pressure difference 256, the CPV may be prevented from beingcommanded from opening and closing, whereas below the threshold pressuredifference 256, the CPV may be commanded to open and close such that theopening and closing events are synchronized with the low pressuredifferences 261 across the CPV as compared to high pressure differences260. It may be further understood that as one or more of the frequency,amplitude and phase of the pressure oscillations changes, so too may thepressure difference threshold. In other words, the pressure differencethreshold may be adjusted as a function of changes in one or more of thefrequency, phase and amplitude of the pressure oscillation wave.

As mentioned above and will be discussed in further detail below, whileinset 250 was discussed with regard to the CPV, the conceptsadditionally apply to the TPCV. In other words, the TPCV may becontrolled to time opening and closing events to coincide with lowpressure differences (e.g. 261) across the TPCV in terms of pressureoscillations (e.g. 252), as compared to high pressure differences (e.g.260) when conducting a fuel tank depressurization operation.

Furthermore, as will be discussed in greater detail below, it is hereinrecognized that under cases where the CPV (or in other examples theTPCV) is indicated to be degraded, or in other words, not sealing asexpected or desired, a cleaning operation may include commanding theopening and closing events of the CPV (or in other examples the TPCV),to coincide with the high pressure differences (e.g. 260) across theparticular valve during purging and/or fuel tank depressurizationoperations. In this way, residual buildup, debris, etc., may be removedfrom the particular valve which may return the valve to a state wheredegradation is not indicated, or in other words where the particularvalve is indicated as sealing as desired or expected.

While synchronizing the PWM signal to the CPV with the frequency andphase of pressure oscillations may improve CPV durability and reduce NVHissues, in hybrid vehicles with limited engine run time opportunitiesfor purging may be limited. Thus, it may be desirable in certain casesto aggressively purge the canister without necessarily synchronizing thePWM signal to the CPV with the frequency and phasing of pressureoscillations, while still avoiding opening/closing the CPV when pressureacross the CPV due to pressure oscillations is greatest. Said anotherway, one way to avoid opening/closing the CPV during a purge event whenpressure across the CPV due to pressure oscillations is greatest may beto immediately command the CPV to a 100% duty cycle (or in other words,command the CPV to a fully open position) in response to a request topurge the canister provided conditions are met for doing so. In thisway, the CPV may be prevented from being opened/closed when pressureacross the CPV is greatest, however such a strategy is not amenable tomost vehicle operating conditions because immediately commanding a 100%duty cycle (without first commanding lower percentage duty cycles) undermost vehicle operating conditions is likely to result in degradedcontrol of engine air/fuel ratio and an increased potential for poordrivability such as engine hesitation, stall, etc.

More specifically, for controlling air-fuel ratio during canisterpurging events to avoid drivability issues related to engine hesitationand/or stall, the duty cycle of the CPV is generally ramped from a lowinitial duty cycle to a high duty cycle over time, based on feedbackfrom an exhaust gas sensor (e.g. 64). In this way, a concentration ofvapors stemming from the canister en route to the engine may be learned,and the learned vapor concentration may be used to adjust fueling to theengine to maintain a desired air-fuel ratio. Furthermore, the learnedvapor concentration may be used to estimate canister loading state.However, there are many situations in hybrid vehicles where the enginemay be deactivated during a purge ramp, prior to the CPV duty cyclereaching a level (e.g. greater than 90% duty cycle) where the canistermay be effectively cleaned of fuel vapors. As one example, a start/stopevent for vehicles equipped with such capability may occur during apurging event, where the engine is shut down when vehicle speed is belowa threshold speed (e.g. at a stop light) and thus the purging operationis discontinued. If the start/stop event occurs prior to the canisterbeing sufficiently cleaned of fuel vapors (e.g. cleaned to less than 5%loaded), then another purging event may be initiated at the nextavailable opportunity, where the ramping procedure is initiated all overagain. Thus, hybrid vehicles with limited engine run time presentchallenges for effectively cleaning the fuel vapor storage canister, andsuch issues may in some examples undesirably result in bleed-emissionsfrom the canister to atmosphere.

Thus, while synchronizing the PWM signal to the CPV during purgingevents may reduce degradation of the CPV over time, there may still beissues related to insufficient canister purging where the vehicleundergoing purging is a hybrid vehicle. Thus, it is herein recognizedthat there are certain examples of vehicle operating conditions forwhich the CPV may be immediately stepped to a 100% duty cycle inresponse to a request for purging the canister. Immediately stepping toa 100% duty cycle may serve to aggressively clean the canister, and mayfurther reduce opportunities where opening and closing the CPV may occurunder conditions where pressure across the CPV due to pressureoscillations is greatest (e.g. 210 a, 210 b, 210 c), which may reducethe potential for CPV degradation.

One such condition where the CPV may immediately be stepped to a 100%duty cycle in response to a request for purging includes a remote startevent where the engine is activated, but there are no occupants in thevehicle. In such a case, even if purging the canister at a 100% CPV dutycycle were to result in engine hesitation or even stall, there would notbe any occupant to notice the issue. For example, in the event of anengine stall, the engine may be rapidly re-activated to combust air andfuel without adverse effects. However, a contingency is that such anexample relies on the exhaust catalyst being above its light-offtemperature so that combusted gasses may be transformed to lesspolluting gasses.

Another such condition includes deceleration fuel shut off (DFSO) eventswhere fueling and spark is discontinued to the engine, but where intakeand exhaust valves continue to operate (e.g. continue to open andclose). In such an example, provided the exhaust catalyst is above itslight-off temperature, the contents of the canister may be purged to theexhaust where the exhaust catalyst transforms the fuel vapors intogasses that are less polluting, even though the fuel vapors are notcombusted. In both examples, the canister may be aggressively purged tothoroughly clean the canister while at the same time reducingopportunities for opening and closing the CPV under conditions wherepressure across the CPV due to pressure oscillations is greatest. Asdiscussed, such cleanings may be particularly desirable for hybridvehicles with limited engine run time, as such vehicles may nototherwise find opportunities to completely purge the canister.

Accordingly, turning now to FIG. 3, a high-level example method 300 isshown for determining whether to aggressively purge the canister or tosynchronize the PWM signal to the CPV with a frequency and phasing ofpressure oscillations across the CPV for a purging event. Specifically,in response to a request to purge the canister, method 300 may includedetermining whether the vehicle is in a condition of a remote start, ora DFSO event. If so, method 300 may proceed to FIG. 4 where method 400may be used to aggressively purge the canister. Alternatively, if aremote start or DFSO event is not indicated, method 300 may be used tosynchronize the PWM signal to the CPV with the frequency and phase ofpressure oscillations across the CPV, in order to purge the canister.If, while the PWM to the CPV is synchronized to the frequency ofpressure oscillations a DFSO event is initiated, then method 300 mayproceed to FIG. 4 where the CPV may be controlled to 100% duty cycle toaggressively purge the canister.

Method 300 will be described with reference to the systems describedherein and shown in FIG. 1, though it should be understood that similarmethods may be applied to other systems without departing from the scopeof this disclosure. Method 300 may be carried out by a controller, suchas controller 12 in FIG. 1, and may be stored at the controller asexecutable instructions in non-transitory memory. Instructions forcarrying out method 300 and the rest of the methods included herein maybe executed by the controller based on instructions stored on a memoryof the controller and in conjunction with signals received from sensorsof the engine system, such as the sensors described above with referenceto FIG. 1. The controller may employ actuators such as fuel injectors(e.g. 45), spark plug (e.g. 53), first oil pressure-controlled actuator(e.g. 183), second oil pressure-controlled actuator (e.g. 184), CPV(e.g. 92), CVV (e.g. 87), FTIV (e.g. 85), throttle (e.g. 42), etc., toalter states of devices in the physical world according to the methodsdepicted below.

Method 300 begins at 305 and includes estimating and/or measuringvehicle operating conditions. Operating conditions may be estimated,measured, and/or inferred, and may include one or more vehicleconditions, such as vehicle speed, vehicle location, etc., variousengine conditions, such as engine status, engine load, engine speed, A/Fratio, manifold air pressure, etc., various fuel system conditions, suchas fuel level, fuel type, fuel temperature, etc., various evaporativeemissions system conditions, such as fuel vapor canister load, fuel tankpressure, etc., as well as various ambient conditions, such as ambienttemperature, humidity, barometric pressure, etc.

Proceeding to 310, method 300 includes indicating whether a canisterpurging event is requested. A canister purging request may be receivedvia the controller 12, in response to an indication of a canisterloading state above a threshold loading state (e.g. greater than 50%full, greater than 60% full, greater than 70% full, etc.), in responseto an indication that a predetermined amount of time has elapsed since aprior canister purging operation, etc. If, at 310, a request forcanister purging is not indicated, method 300 may proceed to 315. At315, method 300 may include maintaining current vehicle operatingconditions. For example, if the vehicle is being operated by one of theengine, motor, or some combination, such operation may be maintained.Method 300 may then end.

Returning to 310, in response to an indication of a request to purge thecanister, method 300 may proceed to 320. At 320, method 300 may includeindicating if the vehicle is in the process of a remote start event. Forexample, upon actuation of a remote start button (e.g. 105) on a key fob(e.g. 104), a remote signal may be transmitted from the key fob and, ifwithin range, received by a remote engine start receiver (e.g. 195) inthe vehicle. Upon receiving the remote signal, the engine start receivermay alert the vehicle controller to start the engine. In other examplesa remote start may be initiated via a cellular telephone, or smartphonebased system where a user's cellular telephone sends data to a serverand the server communicates with the vehicle to start the engine. If, at320 it is indicated that the vehicle is in the process of a remotestart, method 300 may proceed to FIG. 4, where method 400 may be used toaggressively purge the canister.

Alternatively, if at 320 it is indicated that the vehicle is not in theprocess of a remote start event, method 300 may proceed to 325. At 325,method 300 may include indicating whether a request to enter into a DFSOmode of operation has been requested and received via the controller.For example, DFSO entry conditions may be based on various vehicle andengine operating conditions. In particular, the routine may use acombination of one or more of vehicle speed, vehicle acceleration,engine speed, engine load, throttle position, pedal position,transmission gear position, and various other parameters to determinewhether DFSO entry conditions have been met at 325. In one example, whenvehicle-operator demanded torque falls below a predetermined thresholdtorque while the vehicle is being propelled at least in part via theengine, then the engine may enter into the DFSO mode of operation. If,at 325, it is indicated that DFSO mode entry conditions are met, thenmethod 300 may proceed to FIG. 4 where method 400 may be used toaggressively purge the canister.

If, at 325, conditions are not indicated to be met for entering intoDFSO mode, method 300 may proceed to 330. At 330, method 300 may includeindicating whether conditions are met for conducting the requestedcanister purging operation. Conditions being met for conducting acanister purging operation may include an indication of an intakemanifold vacuum greater than a threshold intake manifold vacuum. Thethreshold intake manifold vacuum may include an intake manifold vacuumthat is great enough to enable fuel vapors to be drawn from the fuelvapor storage canister and routed to engine intake. The threshold intakemanifold vacuum may be determined via the MAP sensor (e.g. 39), forexample. Conditions being met for purging the canister at 330 mayfurther include an indication that the engine is combusting air andfuel. Conditions being met for purging the canister at 330 may furtherinclude an indication that a temperature of the emissions control device(e.g. 63) is greater than a light-off temperature, the light-offtemperature comprising a temperature at which the emissions controldevice effectively transforms exhaust gasses into less polluting gasses.

If, at 330, conditions are not indicated to be met for purging thecanister, method 300 may proceed to 315. At 315, method 300 may includemaintaining current vehicle operating conditions. For example, if theengine is not combusting air and fuel and/or if the vehicle is beingpropelled via the motor, such operating conditions may be maintained.The CPV may be maintained closed. Method 300 may then end. However, itmay be understood that the purging operation may be conducted at a nextopportunity when conditions are indicated to be met for conducting thepurging operation.

Returning to 330, in response to conditions being met for conducting thecanister purging operation, method 300 may proceed to 332. At 332,method 300 may indicate whether a CPV cleaning routine has beenrequested. As will be discussed in further detail below, the CPVcleaning routine may be requested in response an indication that the CPVis not sealing as desired or expected (in other words, degradedsealing). If a CPV cleaning routine is requested, method 300 may proceedto FIG. 9, where the canister may be purged and cleaned according to theinstructions at FIG. 9. It may be understood that degraded sealing ofthe CPV may be indicated in response to a fuel system pressure reachinga predetermined negative threshold pressure, with the CPV closed and theCVV closed, under conditions where the engine is operating andcommunicating a vacuum at the CPV. Because the predetermined negativethreshold pressure is reached in the fuel system, the CPV is exhibitingdegraded sealing because if the CPV was not exhibiting degraded sealing,the predetermined negative threshold pressure would not be expected tobe reached in the fuel system.

Alternatively, if a CPV cleaning routine is not requested at 332, method300 may proceed to 335. At 335, method 300 may include determining afrequency, phasing and amplitude of pressure oscillations across theCPV.

In one example, determining a frequency, phasing and amplitude ofpressure oscillations across the CPV may include mapping out ormodelling the frequency, phasing and amplitude of pressure oscillationsbased on one or more pertinent variables which may be available from thecontroller. For example, as discussed above, the amplitude, frequencyand phasing of pressure oscillations across the CPV are a function of atleast engine speed, engine load, cam timing, ambient temperature, enginefiring frequency (forcing frequency), temperature of gas in the intakeand purge line, etc. Engine speed (RPM) may be determined via thecrankshaft position sensor (e.g. 197). Engine load may be determined atleast based on engine speed, mass air flow as determined via the MAFsensor (e.g. 58) and position of the throttle (e.g. 42). Cam timing maybe determined based on position sensors (e.g. 98, 99) configured todetermine position of intake and exhaust valve actuators (e.g. 83, 84),and may be a function of a schedule for controlling the first oilpressure-controlled actuator (e.g. 183) that regulates rotation of theintake camshaft (e.g. 181), and a schedule for controlling the secondoil pressure-controlled actuator (e.g. 184) that regulates rotation ofthe exhaust camshaft (e.g. 182). Ambient temperature may be determinedvia the ambient air temperature sensor (e.g. 107), firing frequency maybe inferred based on fuel injection schedule and spark schedule, andtemperature of gas in the intake and purge line may be indicated via theintake temperature sensor (e.g. 109).

Many of the above variables may be cross-correlated with one another.For example, variable cam timing may be scheduled as a function ofengine speed and load. The engine firing frequency may change inconjunction with engine speed. Thus, based on the information related tothe above-mentioned variables being obtained at the controller, pressureoscillations across the CPV may be inferred since the above-mentionedvariables all affect the frequency, phasing, and amplitude of thepressure oscillations across the CPV.

However, precisely mapping out the frequency, phasing and amplitude ofpressure oscillations across the CPV based on the above-mentionedvariables may be challenging due to the multiple contributing factors.Thus, in one example, a purge line pressure sensor (e.g. 67) may beincluded in the evaporative emissions system, and may be used formapping the frequency, phasing and amplitude of pressure oscillationsand/or for feedback control. More specifically, in terms of feedbackcontrol the above-mentioned variables that contribute to pressureoscillations across the CPV may be mapped out as discussed, and themodeled pressure oscillations may be further updated based on feedbackfrom the purge line pressure sensor. Feedback from the purge linepressure sensor may help to refine the model particularly in terms ofthe phasing of the pressure oscillations.

In another example, the pressure oscillations across the CPV may bedetermined based on two pressure sensors, for example the MAP sensor(e.g. 39) in the intake of the engine and the FTPT (e.g. 23) positionedin the fuel system. In order to rely on such dual sensors to determinepressure oscillations across the CPV, it may be desirable for thecanister-side of the evaporative emissions system (which includes theevaporative emissions system upstream of the CPV) to be at or near (lessthan 2% different) atmospheric pressure. Thus, for vehicles with an FTIV(e.g. 85) where the FTPT is positioned between the fuel tank and theFTIV, the FTIV may be commanded open for determining pressureoscillations across the CPV, which also couples the fuel system toatmosphere via an open CVV (e.g. 87) to relieve pressure in the fuelsystem and evaporative emissions system to atmospheric pressure.Pressure oscillations may be thus be determined as a difference betweenMAP and FTPT, corrected for an offset, the offset comprising a modelledrestriction of the canister buffer section (e.g. 90 a). However, theremay be situations where it is not desirable to couple the evaporativeemissions system to the fuel system via commanding open the FTIV.Examples may include situations where the canister is more than athreshold amount full of fuel vapors, for example when the fuel vaporcanister is saturated with fuel vapors. Thus, in some examples the twopressure sensors relied upon for determining pressure oscillationsacross the CPV may include the MAP sensor and pressure sensor 126positioned in conduit 93 between the FTIV and canister 90.

It may be understood that any one or more of the above-mentionedapproaches may be used, alone or in combination, to determine thefrequency, phasing and amplitude of the pressure oscillations across theCPV.

With the frequency and phasing of the pressure oscillations across theCPV having been determined at 335, method 300 may proceed to 340. At340, method 300 may include synchronizing CPV opening/closing events, orin other words synchronizing the PWM signal to the CPV, with thefrequency and phasing of the pressure oscillations determined at 335.More specifically, step 340 may include setting the threshold pressuredifference (e.g. 256) as a function of the amplitude, frequency andphasing of the pressure oscillations, and then controlling the PWMsignal to the CPV to time opening and closing events of the CPV tocoincide with low pressure differences (e.g. 261) across the CPV, ascompared to high pressure differences (e.g. 260) across the CPV. Asdiscussed above, canister purging events may comprise a strategy where aduty cycle of the CPV is ramped up over time, as a function of feedbackfrom the exhaust gas sensor in order to maintain a desired air-fuelratio during the purging so as to avoid drivability issues. Accordingly,turning to FIG. 5A, an example timeline 500 is depicted, illustratinghow a PWM signal to the CPV may be controlled such that opening/closingevents of the CPV are concurrent with lowest pressure differences acrossthe CPV in terms of the pressure oscillations across the CPV asdetermined at 335 of method 300, while additionally ramping up the dutycycle over time. It may be understood that opening/closing events of theCPV being concurrent with lowest pressure differences may comprise theopening/closing events of the CPV being within a threshold time of thelowest pressure differences.

Example timeline 500 includes plot 505, indicating frequency, phasingand amplitude of pressure oscillations across the CPV, determined forexample as according to step 335 of method 300. As discussed above withregard to FIG. 2, for canister purging events there may be a vacuumacross the CPV, on top of which are the smaller pressure oscillations.Accordingly, pressure across the CPV as depicted at FIG. 5A is negative(−), or more negative (−−−), over time. Timeline 500 further includesplot 510, indicating CPV status (open or closed), over time. Thethreshold pressure difference is indicated as dashed line 511. Whilepressure across the CPV is depicted as negative (−) or more negative(−−−), it may be understood that pressure differences may alternativelybe represented as per inset 250 of FIG. 2, without departing from thescope of this disclosure. As depicted at FIG. 5A, it may thus beunderstood that pressure differences across the CPV are low pressuredifferences 512 as compared to high pressure differences 513, inrelation to the threshold pressure difference 511.

At time t0, it may be understood that a canister purging event isrequested, and frequency, amplitude and phasing of pressure oscillationsacross the CPV have been determined as discussed above with regard tostep 335 of method 300, and the threshold pressure difference 511 hasbeen set. Between time t0 and t1, the CPV is controlled to open andclose at a low initial duty cycle, where the opening and closing eventsof the CPV are concurrent, or coincide, with the points on the pressureoscillation wave (plot 505) that comprise points where pressuredifferences across the CPV are low as compared to high. Solid lines 507represent a threshold range for which the CPV may be opened/closed andstill coincide with the lowest pressure differences across the CPV.Stars 508 depict the opening/closing events of the CPV, for clarity. Byinitiating the CPV opening/closing events at a low duty cycle, thepotential for engine hesitation and/or stall may be reduced. As timegoes on in the purging operation, the concentration of vapor stemmingfrom the canister is learned based on feedback from the exhaust gassensor and the duty cycle is correspondingly increased and air-fuelratio compensated by controlling fuel injection (not shown) to enginecylinders such that a desired air-fuel ratio is maintained over thecourse of the purging.

Accordingly, between time t1 and t2, the duty cycle of the CPV isincreased, while still maintaining opening/closing events concurrentwith the lowest or low pressure differences across the CPV in terms ofthe pressure oscillations.

It may be understood that in order to maintain opening/closing events ofthe CPV concurrent with the low pressure differences across the CPVbetween time t1 and t2, the frequency of opening/closing events may bealtered. In other words, the frequency of PWM signal to the CPVcomprises a first frequency between time t0 and t1, and then is changedto a second frequency between time t1 and t2. Additionally, between timet0 and t1, the CPV is controlled at a first duty cycle, whereas betweentime t1 and t2, the CPV is controlled at a second duty cycle. Clearly,the first duty cycle and the second duty cycles are constrained by theinstructions to time opening and closing events of the CPV with timeswhere pressure differences across the CPV are low in terms of thepressure pulsations across the CPV. In other words, the choice of dutycycle is not arbitrary, but is constrained by the frequency, phasing andamplitude of the pressure pulsations.

This is again seen between time t2 and t3, where the frequency ofopening/closing the CPV changes to a third frequency between time t2 andt3, and where the duty cycle is commanded to change to a third dutycycle between time t2 and t3. Between time t2 and t3, it may be seenthat in order to increase duty cycle, or in other words, increase thetime that the valve stays open for each opening event followed by aclosing event, the frequency changes in order to time CPV opening andclosing events to coincide with low pressure differences in terms of thepressure pulsations across the CPV. Only a portion of the purgingoperation is shown at FIG. 5A for illustrative purposes, but it may beunderstood that after time t3 the duty cycle of the CPV may be furtherincreased, until eventually the duty cycle may comprise a 100% dutycycle. The canister purging operation may proceed in this way untilcanister load is below the threshold load (e.g. less than 5% loaded withfuel vapors), provided that engine operating conditions do not changesuch that canister purging is aborted, such as may occur in a hybridvehicle in response to a start/stop event for example.

Thus, FIG. 5A depicts a situation where frequency of opening/closingevents is equal to or less than the frequency of pressure pulsationsacross the CPV.

Turning to FIG. 5B, another example timeline 525 is illustrated,depicting plot 530, illustrating pressure pulsations across the CPV overtime (similar to the pressure pulsations at FIG. 5A), plot 535,illustrating whether the CPV is open or closed over time, and plot 540,illustrating a voltage commanded to the CPV, or in other words, to asolenoid actuator (not shown) of the CPV, to control opening/closingevents. The voltage command is sent to the CPV based on instructionsfrom the controller (e.g. 12), as a function of desired duty cycle andas a further function of timing opening/closing events of the CPV withthe times of low pressure differences 532 as compared to high pressuredifferences 533 across the CPV during a purging event of the fuel vaporstorage canister, as related to a threshold pressure difference 531.Timeline 525 is similar to timeline 500 in that it depicts a snapshot ofa purge event, illustrating a transitioning from a first frequency ofthe CPV opening/closing events between time t0 and t1 to a secondfrequency of the CPV opening/closing events between time t1 and t2.Accordingly, the duty cycle between time t0 and t1 comprises a first,lower duty cycle, than the second, higher duty cycle between time t1 andt2. Stars 532 represent opening/closing events of the CPV, along thepressure pulsation wave depicted by plot 530. Timeline 525 again depictsan example where frequency of opening/closing events is equal to or lessthan the frequency of pressure pulsations across the CPV.

Between time t0 and t1, the frequency of CPV opening/closing is matchedwith the frequency of pressure pulsations such that each event of thepressure pulsations comprising a low pressure difference across the CPVcoincides with both an opening and closing of the CPV. Accordingly,voltage pulses to the CPV are timed to both open the CPV and then closethe CPV during time periods where pressure is low in terms of thepressure pulsations across the CPV.

Between time t1 and t2, the frequency of opening/closing events of theCPV is lowered to the second frequency, while maintainingopening/closing events coinciding with the times of low pressuredifference across the CPV in terms of the pressure oscillations acrossthe CPV. In this way, the duty cycle of the CPV is increased such thatthe CPV spends more time in the open state between time t1 and t2 ascompared to between time t0 and t1. Between time t1 and t2, it can beseen that voltage is commanded to the CPV to open the CPV, and ismaintained until the next region of low pressure difference across theCPV, when the voltage is stopped from been commanded to the CPV. In thisway, by controlling voltage commands to the CPV, or in other words, bycontrolling voltage commands to the CPV solenoid (not shown), frequencyand duty cycle of the CPV may be controlled as a function of thepressure pulsations across the CPV.

Turning now to timeline 550 at FIG. 5C, it depicts an example timelinefor conducting a purging operation of a fuel vapor storage canisterwhere frequency of CPV pulsing is greater than the frequency of thepressure pulsations across the CPV, such that the frequency of CPVpulsing does not have to be altered in order to increase open time forthe CPV during a purge ramp that may be desired during a purge event ofthe fuel vapors storage canister.

Timeline 550 depicts plot 555, illustrating pressure pulsations acrossthe CPV, over time. It may be understood that the pressure pulsationsare similar in nature to the pressure pulsations depicted at FIG. 2 andFIGS. 5A-5B. Timeline 500 further depicts plot 560, illustrating whetherthe CPV is open, or closed, over time. Plot 565 depicts voltage appliedto the CPV to actuate the CPV open/closed.

Arrow 556 depicts a range (between two lines 558) corresponding to thelow pressure difference across the CPV in terms of the pressurepulsations where it may be desirable to conduct CPV opening/closingevents. The range may be set based on a threshold pressure difference(not shown at FIG. 5C but see for example 531 depicted at FIG. 5B). Thisrange comprises a first range between time t0 and t1, and a second rangebetween time t1 and t2. For clarity, only two opening/closing events ofthe PCV are depicted via plot 560 (solid lines), however plot 560 isillustrated as dashed lines at other regions where the CPV may beopened/closed, but which are not specifically discussed in terms of thevoltage applied to the CPV in order to actuate the CPV open/closed. Forplot 560, lines 561 illustrate regions outside of where the CPV isactually opened, and dashed lines 566 illustrate how voltage is appliedbetween lines 561. Arrows 567 depict points when a duty cycle of the CPVis increased to open the CPV. Between lines 561 and 558, represented asarrow 562, it is illustrated that voltage pulses are applied to the CPV,but do not result in the CPV opening. It is in this way that frequencymay be maintained unchanged while duty cycle is controlled in order tocontrol the CPV opening/closing to coincide with low pressure regions interms of the pressure pulsations across the CPV.

Thus, FIG. 5C is similar to FIG. 5B in that CPV open time is increasedover time, enabling a ramping up of the amount of vapors directed toengine intake during purging of the canister, based on feedback from theexhaust gas sensor. As depicted between time t0 and t1, between lines561 and 558, voltage pulses are applied to the CPV, but they are not ofa duration sufficient to actually open the CPV. While lines 561 aredepicted for illustrative purposes, it may be understood that the shortpulses may occur anywhere along plot 560 where the CPV is not actuallyindicated to be opened. Thus, it may be understood that, between time t0and t1, voltage pulses are repetitively applied to the CPV as depictedbetween lines 561 and 558, at a particular frequency, but that thepulses are of a short enough duration such that the CPV does notactually open. Between lines 558, represented by arrow 556, voltagepulses to the CPV are of a longer duration, or in other words, CPV dutycycle increases, which results in the CPV actually opening within thetime defined by arrows 567. In this way, the CPV is opened at a timecoinciding with low pressure differences across the CPV in terms of thepressure oscillations.

A similar methodology is depicted between time t1 and t2, but the CPV isheld open for an overall greater period of time, such that the CPV opensat one point 557 when pressure across the CPV is low in terms ofpressure pulsations across the CPV, and then closes at another point 559when pressure across the CPV is low in terms of the pressure pulsationsacross the CPV. In this way, CPV duty cycle may change without changingfrequency, where when the CPV is not desired to be opened, the timing ofthe voltage pulse to the CPV is of a short enough duration so as to notresult in the CPV physically opening.

It may be understood that FIG. 5C depicts a short portion of a canisterpurging operation, and it may be further understood that similarmethodology may be used to ramp up an amount of purge vapors directed toengine intake during purging of the canister.

Turning now to FIG. 5D, it depicts another example timeline 575 of acanister purging operation, but where frequency at which the CPV opensis lower than (and not equal to) frequency of the pressure oscillationsacross the CPV. In such an example, the CPV frequency may stay the samewhile a duty cycle is increased over the course of the purgingoperation.

Plot 580 depicts pressure across the CPV, over time. Specifically, asper FIG. 2 and FIGS. 5A-5C, the pressure pulsations across the CPV atplot 580 depict frequency, phasing and amplitude of pressureoscillations across the CPV, determined for example as according to step335 of method 300. As discussed above with regard to FIG. 2, forcanister purging events there may be a vacuum across the CPV, on top ofwhich are the smaller pressure oscillations. Accordingly, pressureacross the CPV as depicted at FIG. 5D is negative (−), or more negative(−−−), over time. Alternatively, plot 580 may instead be depicted as perinset 250 at FIG. 2, without departing from the scope of thisdisclosure. Timeline 575 further includes plot 585, indicating CPVstatus (open or closed), over time, and plot 590, indicating voltagecommanded to the CPV in order to induce CPV opening/closing, over time.Stars 581 depict time points where the CPV opens and/or closes, overtime.

Between time t1 and t2, there are two points where the CPV opens andthen closes, coinciding with (see stars 581) CPV low pressuredifferences across the CPV in terms of the pressure oscillations orpulsations. At time t2, the duty cycle of the CPV is altered, withoutchanging CPV opening frequency. CPV duty cycle is again altered betweentime t3 and t4, such that the duty cycle increases, for the samefrequency of CPV opening. In other words, only the duty cycle is changedin going from the duty cycle between time t2 and t3, to the duty cyclebetween time t3 and t4. Duty cycle is further increased in similarfashion between time t4 and t5.

In this way, when frequency of the CPV is lower than the pressureoscillations across the CPV, duty cycle may be adjusted without changingthe CPV frequency. However, the duty cycle may still be constrained bythe frequency of pressure oscillations across the CPV, such that the CPVis only opened/closed when pressure across the CPV is low in terms ofthe pressure pulsations across the CPV. By increasing duty cycle overtime, a purge ramp process may be conducted, as discussed above, withouthaving to alter frequency of the CPV pulsing.

Thus, FIGS. 5A-5D depict examples of how the CPV may be controlled totime opening/closing events with low pressure differences across the CPVin terms of the pressure pulsations during purging, while still allowingfor a ramping up of the amount of vapors directed to engine intake overtime.

Returning to 340 of method 300, with CPV opening/closing synchronizedwith the frequency and phasing of the pressure oscillations, method 300may proceed to 345. At 345, method 300 includes indicating whether thecanister load is below the threshold canister load. Canister load may beinferred based on the exhaust gas sensor, for example. Morespecifically, when a concentration of vapors being inducted to engineintake from the canister have become such that compensatory adjustmentsto fueling are no longer requested to maintain desired air-fuel ratio,then the controller may infer canister load is below the thresholdcanister load. Additionally or alternatively, a canister temperaturesensor (e.g. 97) may be relied upon to infer when canister load is belowthe threshold canister load. Specifically, the process of fuel vapordesorption via the canister results in heat being consumed and thus thecanister is cooled during purging. Thus, temperature change rate at thecanister as monitored via the canister temperature sensor may be used toinfer when the canister load is below the threshold load. For example,when the temperature change rate is below a threshold temperature changerate (e.g. not changing by more than 5% or less), then it may beindicated that canister load is below the threshold load.

If, at 345, canister load is not indicated to be below the thresholdcanister load, method 300 may proceed to 347. At 347, it may beindicated as to whether a request to enter into a DFSO operational statehas been received by the controller. A DFSO event may be requestedresponsive to a vehicle operator releasing the accelerator pedal forexample, and in response, fuel injection to the engine may be stopped.More specifically, the controller may send a signal to the fuelinjectors, actuating the fuel injectors to cease fuel injection toengine cylinders. Spark may be additionally discontinued. Fuel injection(and spark) may then be reactivated responsive to the vehicle operatordepressing the accelerator pedal, or responsive to engine RPM droppingbelow a predetermined speed (e.g. 2000 RPM or less). During DFSO events,the fuel pump (e.g. 21) may be deactivated as well.

If, at 347, a DFSO event is indicated to be requested, method 300 mayproceed to FIG. 4, where method 400 may be used to aggressively purgethe canister by immediately stepping the CPV duty cycle to 100%,discussed in further detail below. Alternatively, if a DFSO event is notindicated, method 300 may return to step 335, where the frequency,phasing and amplitude of pressure oscillations across the CPV arecontinued to be determined. In other words, during the process ofpurging the canister, frequency, amplitude and phase of pressureoscillations across the CPV may change based on engine operatingconditions and driver demand. Further, the act of purging the canisteritself may influence the frequency, amplitude and phase of the pressureoscillations. As one example, as the process of fuel vapor desorptionfrom the canister results in a cooling effect, temperature of gas in theintake and purge line may change (e.g. become cooler). As temperature ofgas in the intake and purge line is one of the variables mentioned abovethat may influence the frequency and phase of pressure, purging thecanister may alter the frequency and phase of the pressure oscillationsinitially determined at step 335. Thus, it may be understood that thecontroller may continually update the frequency, amplitude and phase ofpressure oscillations across the CPV during the course of any purgingoperation. As frequency, amplitude and phase of the pressureoscillations is continually updated, the controller may continue tocontrol the PWM signal to the CPV at step 340 in order to maintain theCPV opening/closing events in synchrony with the lowest pressuredifferences across the CPV. This may include adjusting the thresholdpressure difference, in order to maintain the CPV opening/closing eventsto coincide with low pressure differences across the CPV as compared tohigh pressure differences in relation to the threshold pressuredifference. Thus, it may be understood that steps 335-347 and returningto step 335 may comprise a feedback loop where frequency, amplitude andphase of pressure oscillations across the CPV are continually updated,and where PWM signal to the CPV is continually controlled to maintainCPV opening and closing events in synchrony with (e.g. correspondingwith instances of) low pressure differences in terms of the pressureoscillations across the CPV.

It may be understood that as frequency, amplitude and phase of pressureoscillations change during the course of a canister purging operation,frequency of the PWM signal to the CPV along with duty cycle may bealtered via the controller in order to maintain CPV opening/closingevents in synchrony with the lowest pressure differences across the CPVin terms of the pressure oscillations.

While not explicitly illustrated, it may be understood that during thecourse of conducting the canister purging operation, if vehicleoperating conditions change such that canister purging is no longerpossible, for example if the engine is stopped in response to astart/stop event, or if vehicle operator requested engine torque changes(e.g. a tip-in event where the accelerator pedal is depressed) such thatintake manifold vacuum is no longer sufficient for canister purging,then the canister purging operation may be aborted.

Returning now to step 345, if while conducting the canister purgingoperation, canister load is indicated to be below the threshold canisterload, method 300 may proceed to 350. At 350, method 300 may includediscontinuing the purging operation. Discontinuing the purging operationmay include commanding the CPV closed. Proceeding to 355, method 300 mayinclude updating vehicle operating conditions. For example, a canisterpurging schedule may be updated to reflect the current loading state ofthe canister. Method 300 may then end.

As depicted at FIG. 3, a remote start (step 320) or a DFSO event maytrigger the controller to purge the canister according to the methoddepicted at FIG. 4. While a remote start event includes vehicleoperating conditions that are distinct from a DFSO event, the method ofaggressively purging the canister according to FIG. 4 in general appliesto both vehicle operating conditions. Accordingly, in discussing method400 depicted at FIG. 4, any differences in how the method is conducteddepending on whether the purging operation is conducted in response to aremote start event or a DFSO event, will be discussed.

Accordingly, proceeding to FIG. 4, it illustrates method 400 which maybe used to aggressively purge the canister under conditions where eitherengine stability issues may be likely to go unnoticed by any vehicleoperator or passenger (e.g. remote start event), or where enginestability issues may be avoided due to the engine not combusting air andfuel (e.g. DFSO event). As method 400 continues from method 300 depictedat FIG. 3, method 400 is described with reference to the system shown inFIG. 1, is carried out by controller 12, and is stored at the controlleras executable instructions in non-transitory memory. Instructions forcarrying out method 400 and the rest of the methods included herein maybe executed by the controller based on instructions stored on a memoryof the controller and in conjunction with signals received from sensorsof the engine system, such as the sensors described above with referenceto FIG. 1. The controller may employ actuators such as fuel injectors(e.g. 45), spark plug (e.g. 53), first oil pressure-controlled actuator(e.g. 183), second oil pressure-controlled actuator (e.g. 184), CPV(e.g. 92), CVV (e.g. 87), FTIV (e.g. 85), throttle (e.g. 42), etc., toalter states of devices in the physical world according to the methodsdepicted below.

Method 400 begins at 405 and includes indicating whether conditions aremet for aggressively purging the canister. Conditions common for both aremote start event and a DFSO event may include an indication that theemissions control device (e.g. 63) is above a desired operatingtemperature (e.g. at or above the light-off temperature), and anindication that intake manifold vacuum is sufficient for purging thecanister. Conditions specific to a remote start event may include anindication that the vehicle is not occupied. Such an indication may beprovided via one or more of seat load cells (e.g. 121), door sensingtechnology (e.g. 122) and/or onboard cameras (e.g. 123).

If, at 405, conditions are not met for aggressively purging thecanister, method 400 may proceed to 410, where current vehicle operatingconditions may be maintained. Method 400 may then end. However, whilenot explicitly illustrated, in some examples, if conditions are not metdue to the emissions control device being at a temperature below thelight-off temperature, method 400 may proceed to 410 where currentvehicle operating conditions are maintained with the exception that anelectric heater (e.g. 119) coupled to the emission control device may beactivated to raise temperature of the emission control device to orabove the light-off temperature. In another example that includes theremote start event, ignition timing may be retarded to rapidly warm theemissions control device, in lieu of or in addition to use of theelectric heater. Accordingly, in such cases, method 400 may return tostep 405 where method 400 includes continuing to query whetherconditions are met for canister purging, indicated by dashed line 411.

Responsive to conditions being met for aggressively purging the canisterat 405, method 400 may proceed to 415. At 415, method 400 may includecommanding closed the throttle (e.g. 42), and may further includecommanding open or maintaining open the CVV. More specifically, thethrottle may be commanded closed in order to increase the amount ofintake manifold vacuum applied to the canister.

Proceeding to 420, method 400 may include commanding the CPV to a 100%duty cycle, or in other words, commanding the CPV fully open. Asdiscussed above, there are a couple benefits to aggressively purging theCPV via immediately stepping to a 100% duty cycle. First is that theramping process of sequentially increasing the duty cycle over time isavoided, thus canister purging may be more rapidly conducted and thusthe potential for the purging operation to be aborted may be reduced.Another is that with the CPV being commanded fully open, issues relatedto opening/closing the CPV at points where pressure across the CPV isgreatest in terms of pressure oscillations may for the most part beavoided. However, when commanded to 100% duty cycle, the CPV has to beopened once, and closed once. There is thus a small possibility that oneof the opening event and/or closing event may coincide with a greatestpressure difference across the CPV in terms of pressure oscillations.Thus, in one example at 420, as it is unlikely that the opening of theCPV will coincide with a time when pressure across the CPV in terms ofpressure oscillations is greatest, the CPV may be commanded fully openwithout attempting to time the opening with a time when pressureoscillations across the CPV are lowest. However, in another example,while not explicitly illustrated, it may be understood that thecontroller may first determine the frequency, amplitude and phase ofpressure oscillations across the CPV as discussed above at step 335, andmay then control CPV opening to coincide with a low pressure differenceacross the CPV in terms of the pressure oscillations. In this way, itmay be ensured that the opening of the CPV will not coincide with apoint on the pressure oscillation wave where pressure across the CPV ishigh.

In either case, with the CPV commanded fully open at 100% duty cycle at420, method 400 may proceed to 425. At 425, method 400 may includeindicating whether canister load is below the threshold canister load.Step 425 may be conducted as described above with regard to step 345 ofmethod 300. If at 425 it is indicated that canister load is below thethreshold canister load, then method 400 may proceed to 430. At 430,method 400 may include discontinuing purging of the canister bycommanding closed the CPV. Similar to that discussed at 420, in oneexample the CPV may be commanded closed without the controller timingthe closing of the CPV with a point on the pressure oscillation wavewhere pressure across the CPV is lowest, as it may be unlikely that theone closing event of the CPV will coincide with a point on the pressureoscillation wave where pressure across the CPV is greatest. However, inother examples, the controller may determine the frequency and phase ofpressure oscillations across the CPV as discussed above at step 335, andmay then control CPV closing to coincide with a lowest pressuredifference across the CPV in terms of the pressure oscillations acrossthe CPV.

With purging discontinued at 430, method 400 may proceed to 435 wherevehicle operating conditions are updated. Specifically, updating vehicleoperating conditions may include updating a canister purging schedule toreflect the current canister loading state. Method 400 may then end.

Returning to 425, in response to canister loading state not yet beingbelow the threshold canister load, method 400 may proceed to 440. At440, method 400 may include indicating if conditions are met fordiscontinuing aggressively purging the canister. For example, if thevehicle is in DFSO mode, in response to a tip-in event where the vehicleoperator requests increased engine torque, conditions may no longer bemet for aggressively purging the canister. In another example thatincludes the remote start event, conditions may no longer be met foraggressively purging the canister in response to the vehicle becomingoccupied and/or in response to an indication of a request for increasedengine torque via a vehicle operator in order to propel the vehicle. Ifsuch conditions are not indicated at 440, then method 400 may return to420 where the CPV may be continued to be commanded fully open at 100%duty cycle, until canister load is below the threshold load.Alternatively, responsive to conditions being met for discontinuingpurging at 440, method 400 may proceed to 445. At 445, purging may bediscontinued by commanding closed the CPV. Similar to that discussed at430, in one example the CPV may be commanded fully closed without takinginto account frequency and phasing of pressure oscillations across theCPV due to the low likelihood of the CPV being commanded closed whenpressure across the CPV in terms of the pressure oscillations isgreatest. However, in another example, the controller may determine thefrequency and phasing of pressure oscillations across the CPV in orderto command closed the CPV at a point on the pressure oscillation wavewhen pressure across the CPV is lowest.

In either case, with the CPV commanded closed at 445, method 400 mayproceed to 450. At 450, method 400 may include updating vehicleoperating conditions. For example, because aggressive purging of thecanister was discontinued prior to canister load being below thethreshold canister load, updating vehicle operating conditions at 450may include indicating current canister loading state, and updating thecanister purging schedule based on the current canister loading state.Method 400 may then end.

While method 400 is depicted as discontinuing purging at 440 in responseto an exit from DFSO mode or in response to the vehicle being occupiedduring a remote start event, it is herein recognized that in anotherexample method 400 may proceed from 440 to step 335 of method 300,without departing from the scope of this disclosure. In other words,rather than discontinuing the purging operation, the CPV duty cycle maybe dropped to as high a duty cycle allowable without resulting in enginestability issues, where the CPV opening and closing events arecontrolled to be synchronous with the lowest pressure differences acrossthe CPV in terms of pressure oscillations across the CPV, as discussedabove.

Turning now to FIG. 6, an example timeline 600 for conducting a canisterpurging operation according to the methods of FIGS. 3-4, is shown.Timeline 600 includes plot 605, indicating whether conditions are met(yes or no) for purging the canister, over time. Timeline 600 furtherincludes plot 610, indicating engine status over time. In this exampletimeline, the engine may be either be off, or rotating in a forwarddirection, the forward direction comprising a direction the enginerotates when combusting air and fuel. Timeline 600 further includes plot615, indicating a status of fuel injection and spark to enginecylinders, over time. Fuel injection and spark may either be provided(on) or not (off). Timeline 600 further includes plot 620, indicatingpressure in the intake of the engine, over time. Timeline 600 furtherincludes plot 625, indicating pressure oscillations across the CPV, overtime. As discussed above, for canister purging events the pressureoscillations across the CPV are on top of a vacuum across the CPV, thusthe pressure oscillations are depicted at being negative (−) or morenegative (−−−) similar to that depicted at FIG. 2. However, it may beunderstood that such pressure oscillations may alternatively be depictedas illustrated at inset 250 of FIG. 2, without departing from the scopeof this disclosure. Dashed line 627 depicts a pressure differencethreshold, set as a function of the frequency, phase and amplitude ofthe pressure oscillations 625, such that the CPV may be timed toopen/close at time of low pressure differences as compared to highpressure differences across the CPV. Lines 626 depict time duration whenthe CPV may be opened/closed to coincide with opening/closing of theCPV, where the time duration is a function of the pressure differencethreshold 627. Timeline 600 further includes plot 630, indicating astatus of the CPV. The CPV may either be fully open or fully closed,over time. Timeline 600 further includes plot 635, indicating a statusof the CVV (fully open or fully closed), over time. Timeline 600 furtherincludes plot 640, indicating a position of the intake throttle, overtime. The throttle may be fully open, fully closed, or somewherebetween. Timeline 600 further includes plot 645, indicating the loadingstate of the fuel vapor canister, over time. Canister loading state mayincrease (+) and decrease (−) over time. Line 646 indicates thethreshold canister load where at or below the threshold canister loadthe canister is considered effectively cleaned of fuel vapors.

At time t0, conditions are indicated to be met for canister purging(plot 605). The engine is rotating in the forward direction (plot 610),and fuel injection and spark is being provided to engine cylinders (plot615). There is a vacuum in the intake manifold (plot 620) of the engine.There are pressure oscillations across the CPV (plot 625) on top of thevacuum across the CPV. At time t0 the CPV is closed (plot 630), and theCVV is open (plot 635). The throttle is in a position based on driverdemand (plot 640), and canister load is high. Thus, at time t0 it may beunderstood that a canister purging event is already in progress, withthe engine combusting air and fuel. The pressure oscillations across theCPV have been determined as described above with regard to step 335 ofmethod 300 and the pressure difference threshold (line 627) has beenset. As discussed, the pressure oscillations are a function of enginefiring frequency, variable camshaft timing, structural componentry ofthe engine and purge line, temperature of gas in the intake and purgeline, engine load, etc. While not explicitly illustrated, it may beunderstood that with the engine combusting air and fuel (plot 615),temperature of the exhaust emission control device (e.g. 63) is at orabove its operating temperature (e.g. light-off temperature).

Between time t0 and t1, timing of the PWM signal to the CPV iscontrolled such that a desired duty cycle is attained, while alsoensuring that the CPV opening and closing events are timed to coincidewith the low pressure differences in terms of the pressure oscillationwave across the CPV. Similar to that depicted at FIG. 5A, linesindicated as 626 depict a range along the pressure oscillation wave forwhen the CPV can be opened or closed in order to coincide with the lowpressure difference across the CPV in terms of the pressureoscillations. In other words, between the two lines denoted as 626, theCPV may be opened or closed in order to coincide with the lowestpressure difference across the CPV in terms of the pressureoscillations. The predetermined time may be adjusted as a function ofthe frequency, phase and/or amplitude of the pressure oscillations, andmay be adjusted in line with adjustments to the pressure differencethreshold which may similarly be adjusted based on frequency, phaseand/or amplitude of the pressure oscillations. For example, thepredetermined time may be shorter in response to the frequencyincreasing while the predetermined time may be increased in response tothe frequency decreasing.

As discussed above, when purging the canister of fuel vapors, the dutycycle of the CPV is generally ramped up over time, and thus it may beunderstood that between time t0 and t1, the CPV duty cycle comprises oneportion of the ramp. In other words, prior to time t0 the CPV duty cycleis less in terms of percentage open time, than in between time t0 andt1. Said another way, the time between time t0 and t1 represents afraction of the overall canister purging operation. For example, asdiscussed above with regard to FIG. 5A, CPV duty cycle may be controlledas a function of the pressure oscillation wave such that the desiredduty cycle may be achieved while also ensuring the CPV opening andclosing events are timed to coincide with the lowest pressuredifferences across the CPV in terms of the pressure oscillation wave.

Between time t0 and t1, canister loading state decreases in accordancewith the vacuum across the CPV drawing fuel vapors from the fuel vaporcanister into the engine for combustion.

At time t1, a DFSO event is initiated and thus fuel injection and sparkto engine cylinders are discontinued (plot 615). In other words, at timet1, it may be understood that the vehicle operator has released theaccelerator pedal to an extent where engine control strategy hasdiscontinued providing fuel and spark to engine cylinders. While notexplicitly illustrated, while the DFSO event initiated at time t1includes stopping providing fuel and spark, intake and exhaust valvescontinue to operate as prior to the initiation of the DFSO event. Inthis way, the engine continues to impart a vacuum on the intake manifoldand evaporative emissions system.

With the DFSO event initiated at time t1, and with canister purgingconditions still indicated to be met, between time t1 and t2, the intakethrottle is commanded to the fully closed position (plot 640). In thisway, an increased vacuum (plot 620) may be provided to the canister foraggressively purging the canister.

At time t2, the CPV is commanded fully open at a 100% duty cycle. Theaction of commanding fully open the CPV, commanding fully closed thethrottle, and operating the engine in DFSO mode results in a change inpressure oscillations in the purge line (plot 625), however because theCPV is commanded to the 100% duty cycle there is no compensatory controlstrategy in terms of PWM signal to the CPV in terms of the change inpressure oscillations.

Between time t2 and t3, the canister is aggressively purged as intakemanifold vacuum increases, and with the CPV fully open at 100% dutycycle. Accordingly, by time t3, canister load reaches the thresholdcanister load represented by line 646. It may be understood that in thisexample timeline, while not explicitly illustrated, temperature of theemission control device (e.g. 63) remained above the light-offtemperature for the duration between time t2 and t3. Accordingly, eventhough the engine is not combusting air and fuel during the DFSO eventwhile the canister is being purged, the purged fuel vapors are convertedto less polluting gasses by the emission control device.

At time t3, with the canister load having reached the threshold canisterload indicating that the canister is clean, conditions are no longerindicated to be met for canister purging (plot 605). The CPV iscommanded fully closed (plot 630). Between time t3 and t4, the throttleis controlled to the position it was in prior to the DFSO event beinginitiated. At time t4, the controller receives a request for increasedengine torque via the vehicle operator depressing the accelerator pedal,and accordingly, fuel injection and spark are resumed being provided tothe engine (plot 615). After time t4, the vehicle is propelled via theengine and a canister purging schedule is updated to reflect the currentloading state of the canister.

While the above-depicted example methodology and timelines depictcontrolling the CPV such that opening/closing events are timed tocoincide with low pressure differences in terms of pressure oscillationsacross the valve during purging, it is herein recognized that in someexamples it may be desirable to control another valve, namely the fueltank pressure control valve (TPCV) (e.g. 125), in similar fashion forconducting fuel tank depressurization during select vehicle operationalconditions. Such methodology will be discussed below with regard to FIG.7.

Thus, discussed herein, a method may comprise purging a fuel vaporcanister that captures and stores fuel vapors from a fuel system of avehicle by synchronizing a timing of opening and closing events of acanister purge valve to correspond with instances where a pressuredifference across the canister purge valve is lower as compared tohigher in terms of pressure oscillations across the canister purge valveduring purging the fuel vapor canister.

Such a method may further comprise adjusting the timing of the openingand the closing events of the canister purge valve in response tochanges in the pressure oscillations across the canister purge valveduring purging the fuel vapor canister.

Such a method may further comprise controlling a duty cycle of thecanister purge valve while synchronizing the timing of the opening andthe closing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillations.

In such a method, the pressure oscillations may be a function of atleast operating conditions of an engine that receives purge gasses fromthe fuel vapor canister. Such a method may thus further comprisedetermining a frequency, a phase, and an amplitude of the pressureoscillations across the canister purge valve in order to synchronize thetiming of the opening and the closing events of the canister purge valveto correspond with the instances where the pressure differences acrossthe canister purge valve are lower as compared to higher in terms of thepressure oscillations.

In such a method, determining the frequency, the phase and the amplitudeof the pressure oscillations may include mapping the pressureoscillations based on one or more of at least an engine speed, an engineload, a timing of opening and/or closing of intake and/or exhaust valvesof the engine, and an ambient temperature. Determining the frequency,the phase and the amplitude of the pressure oscillations may be based atleast in part on feedback from a pressure sensor at the canister purgevalve. In some examples, determining the frequency, the phase, and theamplitude of the pressure oscillations may be based at least in part ona difference between an engine intake pressure and a fuel systempressure with the fuel system coupled to atmosphere, corrected for anoffset that may be modelled as a function of a restriction of a buffersection of the fuel vapor canister.

In such a method, synchronizing the timing of the opening and theclosing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillationsacross the canister purge valve may further comprise controlling a pulsewidth modulation signal to the canister purge valve based on thepressure oscillations across the canister purge valve.

In such a method, synchronizing the timing of the opening and theclosing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillationsacross the canister purge valve may improve durability and may reduceissues related to noise, vibration and harshness of the canister purgevalve.

In such a method, synchronizing the timing of the opening and theclosing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillationsacross the canister purge valve may further comprise controlling thecanister purge valve to open and/or close within a threshold timeduration in relation to the pressure oscillations across the canisterpurge valve, the threshold time duration corresponding to when thepressure difference is lower as compared to higher in terms of thepressure oscillations across the canister purge valve.

Another example of a method for a hybrid vehicle comprises reducingdegradation and issues related to noise, vibration and harshness of acanister purge valve by timing opening and closing events of thecanister purge valve to coincide with when a pressure difference acrossthe canister purge valve is lower than a threshold pressure differencein terms of pressure oscillations across the canister purge valve whilepurging a fuel vapor canister of fuel vapors.

In such a method, the threshold pressure difference may be determined asa function of the pressure oscillations across the canister purge valve.The threshold pressure difference may be updated as the pressureoscillations change during the course of purging the fuel vapor canisterof fuel vapors. In such a method, the method may further comprisedetermining a frequency, a phase and an amplitude of the pressureoscillations across the canister purge valve and controlling a pulsewidth modulation signal to the canister purge valve in order tosynchronize the timing of the opening and the closing of the canisterpurge valve to coincide with when the pressure difference across thecanister purge valve is lower than the threshold pressure difference interms of the pressure oscillations across the canister purge valve.

In such a method, reducing degradation and issues related to noise,vibration and harshness of the canister purge valve may further comprisecommanding the canister purge valve fully open without first commandinglower percentage duty cycles in response to a request for purging thefuel vapor canister, under select vehicle operating conditions. In sucha method, the select vehicle operating conditions may include a remotestart event of an engine of the vehicle, where the vehicle is indicatedto be unoccupied and where an exhaust catalyst is at or above anoperating temperature of the exhaust catalyst. In such a method, theselect vehicle operating conditions may include a deceleration fuelshut-off event where fueling to an engine of the vehicle is shut off butwhere intake and exhaust valves of the engine continue to open andclose, and where an exhaust catalyst is at or above an operatingtemperature of the exhaust catalyst.

Turning to FIG. 7, a high-level example method 700 is shown forcontrolling the TPCV to depressurize the fuel system or fuel tank, whenconditions are met for doing so. The controlling of the TPCV may becarried out in similar fashion to that discussed above for controllingthe CPV during canister purging operations. Such a method may beapplicable to vehicles with sealed fuel tanks, such as the fuel tankdepicted at FIG. 1, in which the FTIV may be commanded closed to sealthe fuel tank from the evaporative emissions system, and where he TPCVmay additionally be commanded closed to seal the fuel tank. It may beunderstood that method 700 may be used to depressurize the fuel tank androute any vapors stemming from the fuel system to engine intake forcombustion.

Method 700 will be described with reference to the systems describedherein and shown in FIG. 1, though it should be understood that similarmethods may be applied to other systems without departing from the scopeof this disclosure. Method 700 may be carried out by a controller, suchas controller 12 in FIG. 1, and may be stored at the controller asexecutable instructions in non-transitory memory. Instructions forcarrying out method 700 and the rest of the methods included herein maybe executed by the controller based on instructions stored on a memoryof the controller and in conjunction with signals received from sensorsof the engine system, such as the sensors described above with referenceto FIG. 1. The controller may employ actuators such as fuel injectors(e.g. 45), spark plugs (e.g. 53), first oil pressure-controlled actuator(e.g. 183), second oil pressure-controlled actuator (e.g. 184), CPV(e.g. 92), CVV (e.g. 87), FTIV (e.g. 85), throttle (e.g. 42), TCPV (e.g.125), etc., to alter states of devices in the physical world accordingto the methods depicted below.

Method 700 begins at 705 and includes estimating and/or measuringvehicle operating conditions. Operating conditions may be estimated,measured, and/or inferred, and may include one or more vehicleconditions, such as vehicle speed, vehicle location, etc., variousengine conditions, such as engine status, engine load, engine speed, A/Fratio, manifold air pressure, etc., various fuel system conditions, suchas fuel level, fuel type, fuel temperature, etc., various evaporativeemissions system conditions, such as fuel vapor canister load, fuel tankpressure, etc., as well as various ambient conditions, such as ambienttemperature, humidity, barometric pressure, etc.

Proceeding to step 710, method 700 includes indicating whetherconditions are met for fuel tank (or fuel system) depressurization.Conditions being met may comprise one or more of the following. Forexample, conditions being met for fuel tank depressurization may includean indication that fuel tank pressure is greater than a thresholdpressure. The threshold pressure may comprise a preset thresholdpressure, for example. Conditions being met at 710 may in some examplesinclude an indication that the canister is clean (canister loaded lessthan 5% full, or less than 10% full), because the canister purge valvemay be commanded open 100% in order to route fuel vapors to engineintake for combustion. Conditions being met at 710 may include anindication that the engine is in operation combusting air and fuel.Conditions being met at 710 may include an indication that the exhaustcatalyst (e.g. 63) is at or above its operating temperature, orlight-off temperature.

If, at 710, conditions are not indicated to be met for conducting thefuel tank depressurization routine, then method 700 may proceed to 715.At 715, method 700 may include maintaining current vehicle operatingconditions. For example, the fuel tank may be maintained sealed, engineoperation may continue as per driver demand, etc. Method 700 may thenend.

Returning to 710, in response to conditions being met for fuel tankdepressurization, method 700 may proceed to 720. At 720, method 700 mayinclude commanding the CPV to 100% duty cycle. In other words, the CPVmay be commanded to a fully open position. Continuing to 725, method 700may include determining the frequency, phasing, and amplitude ofpressure pulsations at the TPCV.

Similar to that discussed above for the CPV, pressure oscillationsacross the TPCV may vary based on several factors. One such factor isforcing frequency, or engine firing frequency. Engine forcing frequencymay vary with engine speed. Another such factor relates tophasing/timing changes when VCT is used to alter intake valve timing.Another such factor may be related to whether standing waves develop orare present in the fluidically coupled fuel system and evaporativeemissions system (including the conduit that connects the evaporativeemissions system to engine intake). A further such factor relates totemperature of gas in the fuel system/evaporative emissions system, astemperature affects the speed and propagation of pressure waves.

As mentioned above with regard to FIG. 3, engine speed (RPM) may bedetermined via the crankshaft position sensor (e.g. 197). Engine loadmay be determined at least based on engine speed, mass air flow asdetermined via the MAF sensor (e.g. 58) and position of the throttle(e.g. 42). Cam timing may be determined based on position sensors (e.g.98, 99) configured to determine position of intake and exhaust valveactuators (e.g. 83, 84), and may be a function of a schedule forcontrolling the first oil pressure-controlled actuator (e.g. 183) thatregulates rotation of the intake camshaft (e.g. 181), and a schedule forcontrolling the second oil pressure-controlled actuator (e.g. 184) thatregulates rotation of the exhaust camshaft (e.g. 182). Ambienttemperature may be determined via the ambient air temperature sensor(e.g. 107), firing frequency may be inferred based on fuel injectionschedule and spark schedule, and temperature of gas in the intake andpurge line may be indicated via the intake temperature sensor (e.g.109).

Many of the above variables may be cross-correlated with one another.For example, variable cam timing may be scheduled as a function ofengine speed and load. The engine firing frequency may change inconjunction with engine speed. Thus, based on the information related tothe above-mentioned variables being obtained at the controller, pressureoscillations across the TPCV may be inferred since the above-mentionedvariables all affect the frequency, phasing, and amplitude of thepressure oscillations across the TPCV.

However, similar to that discussed above at FIG. 3, precisely mappingout the frequency, phasing and amplitude of pressure oscillations acrossthe TPCV based on the above-mentioned variables may be challenging dueto the multiple contributing factors. Thus, in one example, a pressuresensor (e.g. 126) may be included in the evaporative emissions system(for example in the conduit between the fuel tank and the canister), andmay be used for mapping the frequency, phasing and amplitude of pressureoscillations and/or for feedback control. More specifically, in terms offeedback control the above-mentioned variables that contribute topressure oscillations across the TPCV may be mapped out as discussed,and the modeled pressure oscillations may be further updated based onfeedback from the pressure sensor positioned in the conduit between thefuel tank and the canister. Feedback from the pressure sensor (e.g. 126)may help to refine the model particularly in terms of the phasing of thepressure oscillations.

In another example, the pressure oscillations across the TPCV may bedetermined based on two pressure sensors, for example the pressuresensor (e.g. 126) positioned in the conduit (e.g. 93) between the fueltank and the canister, and the FTPT (e.g. 23). For example, pressureoscillations may be determined based on a difference between pressuresensor (e.g. 126) and FTPT (e.g. 23) minus an offset, the offset, theoffset comprising a modeled restriction in the canister's buffer (e.g.90 a) region.

It may be understood that any one or more of the above-mentionedapproaches may be used, alone or in combination, to determine thefrequency, phasing and amplitude of the pressure oscillations across theCPV.

With the frequency and phasing (and amplitude) of the pressureoscillations across the TPCV having been determined at 725, method 700may proceed to 730. At 730, method 700 may include synchronizing TPCVopening/closing events, or in other words synchronizing the PWM signalto the TPCV, with the frequency and phasing of the pressure oscillationsdetermined at 725. Similar to that discussed above at FIG. 3,synchronizing the PWM signal to the TPCV may include commanding openingand closing events of the TPCV to coincide with low pressure differencesacross the TPCV in terms of the pressure oscillations across the TPCV.Thus, a pressure difference threshold similar to that discussed at FIGS.2-3 may be set, such that it may readily be determined when the TPCV maybe commanded open/closed to coincide with the low pressure differencesacross the TPCV as compared to high pressure differences.

As discussed above, fuel system depressurization events may comprise astrategy where a duty cycle of the TPCV is ramped up over time, as afunction of feedback from the exhaust gas sensor in order to maintain adesired air-fuel ratio during the purging so as to avoid drivabilityissues. Thus, while not explicitly illustrated, at 730 it may beunderstood that synchronizing TPCV opening/closing events may includeramping up an amount of fuel vapor that is routed to engine intake forcombustion, over time, similar to that discussed above regarding theCPV. Specifically, the concepts discussed above with regard to FIGS.5A-5D relate similarly to the TPCV, and thus for brevity the conceptswill not all be further described. However, it may be understood that,similar to the CPV, controlling the TPCV to open/close at times whenpressure across the TPCV is low in terms of pressure pulsations acrossthe TPCV may include altering frequency, phasing, and duty cycle of theTPCV to ramp up the amount of vapors directed to engine intake over thecourse of the fuel system depressurization event. In this way, byramping up the amount of vapors directed to engine intake over time,opportunity for engine hesitation and/or stall due to inhalation by theengine of an overly rich mixture, may be reduced or avoided.

Proceeding to 735, method 700 may include indicating whether fuel tankpressure is below a predetermined threshold pressure. For example, thepredetermined threshold may comprise a pressure that is within athreshold (e.g. within 10% or less, or within 5% or less) of atmosphericpressure. If the fuel tank pressure has not yet reached thepredetermined threshold, then method 700 may include continuing todetermine the frequency, phasing and amplitude of the pressurepulsations across the TPCV. In other words, frequency, phase andamplitude of the pressure pulsations may continually change depending ondriver demand, and accordingly, in order to synchronize the TPCV openingand closing events to points of low pressure across the TPCV as comparedto high pressure, the frequency, amplitude and phasing of the pressureoscillations may also have to be continually updated until the fuel tankpressure has reached the predetermined threshold pressure.

In response to the fuel tank pressure being indicated to be less than orequal to the predetermined threshold pressure, method 700 may proceed to740, where the CPV and TPCV may be commanded closed. Proceeding to 745,method 700 may include updating vehicle operating conditions, to reflectthe recent fuel tank depressurization routine. For example, updatingvehicle operating conditions may include updating a canister loadingstate, updating fuel system pressure, etc. Method 700 may then end.

Turning now to FIG. 8, an example timeline 800 for conducting a fueltank depressurization routine, according to the method depicted at FIG.7, is shown. Timeline 800 includes plot 805, indicating whetherconditions are met for depressurizing the fuel tank (yes), or not (no),over time. Timeline 800 further includes plot 810, indicating enginestatus, over time. In this example timeline, the engine may be rotatingin a forward direction, or may be off. Timeline 800 further includesplot 815, indicating whether fuel injection and spark are being providedto engine cylinders (on) or not (off), over time. Thus, it may beunderstood that when the engine is rotating in the forward direction(plot 810), with fuel injection and spark being provided (on), then theengine is combusting air and fuel. Timeline 800 further includes plot820, indicating pressure in the intake manifold of the engine. Pressuremay be, in this example timeline, atmospheric pressure or less thanatmospheric (vacuum). Timeline 800 further includes plot 825, indicatingdetermined pressure pulsations across the TPCV, over time. The pressurepulsations may increase (+) such that the pressure difference isgreater, or may decrease (−) such that the pressure difference is lower.Thus, in this example timeline, the pressure oscillations are depictedin similar fashion as inset 250, where the pressure oscillations aresimply depicted as being greater or lesser, over time. At times whenpressure oscillations are not relevant and/or not requested to be known,then the pressure oscillations may not be applicable (n/a), and when notapplicable, plot 825 is represented as a dashed line, as opposed to asolid line. Double lines 826 are used to illustrate that points of lowpressure in terms of the pressure oscillations correspond toopening/closing events of the TPCV at plot 830. A pressure differencethreshold 827 may be set based on the frequency, phasing and amplitudeof the pressure oscillations, such that the controller may be able totime TPCV opening and closing events to coincide with low pressuredifferences 828 as compared to high pressure differences 829 across theTPCV. Only one set of double lines 826 are indicated, and stars are usedto indicate when TPCV opening/closing events occur in relation to thepressure pulsations across the TPCV. Accordingly, plot 830 depicts TPCVstatus (open or closed), over time.

Timeline 800 further includes plot 835, indicating a status of the CPV,and plot 840, indicating a status of the CVV, over time. For both plot835 and plot 840, the valves may be either open or closed, over time.Timeline 800 further includes plot 845, indicating a loading state ofthe fuel vapor storage canister, over time. Canister load may eitherincrease (+) or decrease (−), over time. Timeline 800 further includesplot 850, indicating fuel tank pressure, over time. Fuel tank pressuremay either increase (+) or decrease (−), over time.

At time t0, conditions are not yet met for fuel tank pressure relief(plot 805). The engine is combusting air and fuel (see plots 810 and815), and engine intake manifold vacuum is below a threshold vacuum,represented by dashed line 821. With engine intake manifold vacuum beingbelow the threshold vacuum, it may be understood that fuel vapors may bedrawn from the fuel tank to engine intake. Pressure pulsations acrossthe TPCV have not yet been determined (plot 825), as conditions have notyet been met for conducting the fuel tank depressurization routine. TheCPV is closed (plot 835), and the CVV is open (plot 840). Canister loadis low (plot 845), being below the threshold canister load (e.g. below10% full of vapors, or below 5% full of vapors, etc.), the thresholdcanister load represented by dashed line 846. Furthermore, there ispositive pressure (+) in the fuel tank (plot 850) as compared toatmosphere, although because fuel tank pressure is below a first fueltank pressure threshold (represented by dashed line 851), conditions forfuel tank pressure relief are not yet indicated to be met (see plot805).

At time t1, fuel tank pressure (plot 850) rises above the first fueltank pressure threshold (line 851). Accordingly, it is determined attime t1 that conditions are met for conducting the fuel tankdepressurization routine (plot 805), and the CPV is commanded open.Between time t1 and t2, pressure pulsations across the TPCV aredetermined, as discussed above with regard to step 725 of method 700. Attime t2, the pressure pulsations have been determined, and between timet2 and t3, the TPCV is controlled to time opening and closing events inline with time of low pressure in terms of the pressure oscillations,represented as stars. The TPCV is controlled accordingly between time t2and t3.

At time t3, the timing of opening and closing events is altered (e.g.frequency and phasing altered) in order to route a greater amount ofvapors from the fuel tank to engine intake. In other words, the dutycycle of the TPCV is increased, beginning at time t3. While notexplicitly illustrated, it may be understood that increasing the dutycycle is in response to the exhaust gas sensor being used to estimatethe concentration of fuel vapors stemming from the fuel tank, such thatair-fuel ratio may be controlled to prevent engine hesitation and/orstall and to maintain desired air-fuel ratio during the depressurizationevent. The TPCV is controlled as such for the duration of time betweentime t3 and t4. At time t4, the timing of opening and closing events isonce again altered so as to further increase the duty cycle of the TPCVto allow for further fuel tank depressurization. Once again, thealtering of the timing is in response to the exhaust gas sensor beingused to estimate a fuel vapor concentration stemming from the fuel tank,such that it is determined that the duty cycle can be increased withouta great risk for engine stall or hesitation.

Between time t4 and t5, fuel tank pressure continues to decline, and attime t5, fuel tank pressure reaches the second fuel tank pressurethreshold. With fuel tank pressure having reached the second fuel tankpressure threshold, conditions are no longer indicated to be met forfuel tank pressure depressurization (plot 805). Accordingly, the CPV iscommanded closed (plot 835), as is the TPCV (plot 830). After time t5,it is no longer applicable to measure pressure pulsations across theTPCV (plot 825).

While the above methodologies relate to timing CPV or TPCVopening/closing events to coincide with low pressure differences acrossthose valves in terms of pressure oscillations, it is herein recognizedthat there may be opportunity to at least transiently time opening andclosing of the CPV (and in some cases the TPCV), to coincide with highpressure differences in terms of pressure oscillations, which may resultin the valve being cleaned. The description below relates to conductingsuch a cleaning operation of the CPV, however it may be understood thatsimilar methodology may equally apply to the TPCV, without departingfrom the scope of this disclosure.

Returning to FIG. 3, in response to CPV cleaning being requested at 332,method 300 may proceed to FIG. 9. At 905, method 905 includesdetermining the frequency, amplitude and phase of pressure oscillationsacross the CPV, in the same manner as was previously discussed for step335 of method 300. Accordingly, a pressure difference threshold may beset, similar to that discussed at FIG. 3, to differentiate between highand low pressure differences in terms of the pressure oscillationsacross the CPV. Next, method 900 may proceed to 910, where CPV openingand closing times are first synchronized to low pressure differencesacross the CPV in terms of the pressure oscillations. In other words,step 910 may be conducted in similar fashion as step 340 of method 300.In this way, the canister may begin being purged with CPV opening andclosing events timed to coincide with low pressure differences in termsof the pressure oscillations across the CPV, similar to that discussedat FIG. 3. The CPV may be controlled in such fashion for a predeterminedtime duration, a predetermined number of opening and/or closing events,etc.

Proceeding to 915, method 900 may include transitioning the CPVopening/closing events to be timed to coincide with high pressuredifferences across the CPV in terms of the pressure oscillations,instead of with the low pressure differences. By timing the CPVopening/closing events to coincide with high pressure differences acrossthe CPV, carbon deposits, dust, debris, etc., which may be preventingthe CPV from closing as expected or desired, may be dislodged, thusresulting in the CPV once again properly sealing. This action of timingthe CPV opening/closing events may for a short length of time, result inan increase in noise, vibration and harshness (NVH). The CPV may becontrolled in such fashion for a predetermined duration of time, for apredetermined number of CPV opening/closing events, etc. It may beunderstood that, in transitioning from the CPV opening/closing eventscoinciding with low pressure to CPV opening/closing events coincidingwith high pressure in terms of the pressure oscillations, frequency andduty cycle may be maintained the same. An exception is if it is desiredto change duty cycle, for example, at a similar time as it is desired tochange from timing opening/closing events at low pressure to timingopening/closing events at high pressure differences across the CPV. Insuch an example, the CPV may be transitioned to a different duty cycleand transitioned from opening/closing at low pressure differences toopening/closing at high pressure differences, simultaneously. Such anexample may occur if the duty of the CPV is being ramped up during thecourse of a canister purging event, as discussed above. The samediscussion regarding how to transition from timing opening/closingevents to coincide with low pressure differences across the CPV, totiming opening/closing events to coincide with high pressure differencesacross the CPV, equally applies to transitioning from timingopening/closing events at high pressure differences to timingopening/closing events at low pressure differences in terms of thepressure oscillations across the CPV.

After the CPV has been duty cycled to open and close at times coincidingwith high pressure differences across the CPV, for the predeterminedduration or number of opening/closing events, etc., method 900 mayproceed to 920, where the CPV opening/closing events are once againsynchronized to the coincide with low pressure differences across theCPV in terms of the pressure oscillations. Clearly, while not explicitlyillustrated, it may be understood that the frequency, phasing andamplitude of the pressure oscillations may change during the conductingof the canister purging/CPV cleaning operation, and accordingly, it maybe understood that such parameters may continually be determined andupdated so that the timing of opening/closing events of the CPV may bemaintained to coincide with either low pressure differences, or highpressure differences in terms of the pressure oscillations.

Proceeding to 925, method 900 may include indicating whether canisterload is less than the threshold canister load. Learning of the canisterload may be based on the exhaust gas sensor, temperature sensor(s)positioned in the canister, etc., as discussed above with regard to step345 at FIG. 3. If, at 925, canister load is not below the thresholdcanister load, then method 900 may proceed to 930. At 930, method 900may include indicating whether additional cleaning is requested. In someexamples, a number of cleaning operations to be conducted during asingle purging operation may be stored at the controller, and may bebased on a degree to which the CPV was previously indicated to not befunctioning as desired. For example, one way in which the CPV may bedetermined to not be sealing properly may include commanding closed theCVV, commanding closed the CPV, and with the engine combusting air andfuel, indicating if vacuum develops in the fuel system. For example, apressure sensor (e.g. 126) may be used to monitor vacuum build. Ifvacuum does build to a level greater than a predetermined negativepressure threshold, then it may be determined that the CPV is notproperly sealing, as otherwise engine intake manifold vacuum would nothave been expected to reach the fuel system. The level of vacuumattained may be a function of how degraded the CPV is, and may be afunction of engine manifold vacuum level. Thus, based on a level ofvacuum build in the fuel system over a predetermined time period whenconducting such a test, a level to which the CPV is degraded may beindicated. The more degraded (greater the vacuum) the CPV, the moretimes the cleaning routine may be conducted during a single canisterpurging event.

Accordingly, at 930, if additional cleaning is requested, method 900 mayreturn to 915, where once again the CPV opening/closing events may betimed to coincide with high pressure differences across the CPV in termsof the pressure oscillations. Alternatively, at 930, if additionalcleaning is not requested, then method 900 may return to 920, where CPVopening/closing events may be maintained to coincide with low pressuredifferences across the CPV in terms of the pressure oscillations.

Returning to 925, in response to canister load being indicated to beless than the threshold canister load, method 900 may proceed to 935. At935, method 900 may include discontinuing purging of the canister.Discontinuing purging may include commanding the CPV closed. Proceedingto 940, method 900 may include updating vehicle operating conditions.Updating vehicle operating conditions may include updating the loadingstate of the canister, and may further include scheduling a follow-uptest to determine whether the cleaning routine conducted on the CPV,resulted in the CPV once again sealing properly, as expected.

Accordingly, turning now to FIG. 10, a high-level example method 1000for determining whether a CPV cleaning routine, as discussed at FIG. 9,successfully resulted in the CPV once again sealing as expected ordesired, is shown. Method 1000 will be described with reference to thesystems described herein and shown in FIG. 1, though it should beunderstood that similar methods may be applied to other systems withoutdeparting from the scope of this disclosure. Method 1000 may be carriedout by a controller, such as controller 12 in FIG. 1, and may be storedat the controller as executable instructions in non-transitory memory.Instructions for carrying out method 1000 and the rest of the methodsincluded herein may be executed by the controller based on instructionsstored on a memory of the controller and in conjunction with signalsreceived from sensors of the engine system, such as the sensorsdescribed above with reference to FIG. 1. The controller may employactuators such as fuel injectors (e.g. 45), spark plug (e.g. 53), CPV(e.g. 92), CVV (e.g. 87), FTIV (e.g. 85), throttle (e.g. 42), TCPV (e.g.125), etc., to alter states of devices in the physical world accordingto the methods depicted below.

Method 1000 begins at 1005 and includes estimating and/or measuringvehicle operating conditions. Operating conditions may be estimated,measured, and/or inferred, and may include one or more vehicleconditions, such as vehicle speed, vehicle location, etc., variousengine conditions, such as engine status, engine load, engine speed, A/Fratio, manifold air pressure, etc., various fuel system conditions, suchas fuel level, fuel type, fuel temperature, etc., various evaporativeemissions system conditions, such as fuel vapor canister load, fuel tankpressure, etc., as well as various ambient conditions, such as ambienttemperature, humidity, barometric pressure, etc.

Proceeding to 1010, method 1000 includes indicating whether a CPVcleaning routine has been recently conducted, for which the success ofthe cleaning routine has not yet been ascertained. If not, method 1000may proceed to 1015, where current vehicle operating conditions may bemaintained without conducting a CPV diagnostic to ascertain whether theCPV cleaning routine was successful or not. Method 1000 may then end.

Returning to 1010, if the CPV cleaning diagnostic was recently conductedfor which a CPV diagnostic test to determine whether the cleaningroutine was successful or not is scheduled (but not yet conducted), thenmethod 1000 may proceed to 1020. At 1020, method 1000 may includeindicating whether conditions are met for conducting the CPV diagnostic.Conditions being met at 1020 may include one or more of the following.Conditions being met may include an indication that the engine is inoperation, combusting air and fuel. Conditions being met may include anindication of an engine intake manifold vacuum greater than apredetermined threshold vacuum, the threshold vacuum comprising a vacuumsufficient to conduct the diagnostic. Conditions being met at 1020 mayinclude steady-state conditions, for example engine idle or steady-statecruising conditions to avoid fuel slosh events, etc. Conditions beingmet at 1020 may include an indication of an absence of undesiredevaporative emissions stemming from the vehicle fuel system and/orevaporative emissions system.

If, at 1020, conditions are not yet met for conducting the CPVdiagnostic, method 1000 may proceed to 1025. At 1025, method 1000 mayinclude maintaining current vehicle operating conditions untilconditions are met for conducting the CPV diagnostic.

In response to conditions being indicated to be met for conducting theCPV diagnostic at 1020, method 1000 may proceed to 1030. At 1030, method1000 may include commanding closed the CVV, and commanding closed theCPV. Proceeding to 1035, method 1000 may include monitoring fuel systemvacuum for a predetermined duration. In one example, the pressure sensor(e.g. 126) positioned between the FTIV and the canister may be utilizedto monitor fuel system vacuum. In this way, the fuel tank may bemaintained sealed for the CPV diagnostic. In other examples, the FTIVmay be commanded open, and the FTPT (e.g. 23) may be relied upon formonitoring fuel system vacuum.

Continuing to 1040, if the fuel system vacuum is not indicated to begreater than a predetermined threshold vacuum, then method 1000 mayproceed to 1045, where it may be indicated that the CPV is functioningas desired. In other words, it may be indicated that the CPV cleaningoperation was successful in that it restored the ability of the CPV toseal as expected. Said another way, the CPV sealing as expected includesthe CPV preventing engine manifold vacuum from drawing a vacuum on thefuel system, when the CPV is closed. With the CPV indicated to befunctioning as desired, the CVV may be commanded open. Proceeding to1050, vehicle operating parameters may be updated. For example, updatingvehicle operating parameters may include removing a flag that waspreviously set at the controller to indicate a pending status as towhether the CPV is functioning as desired. More specifically, thevehicle may illuminate a malfunction indicator light (MIL) for adegraded CPV after the CPV fails to pass a CPV diagnostic twice(corresponding to two trips or drive cycles). Thus, in response to afirst attempt at diagnosing the CPV where the CPV doesn't pass, a MILmay not be illuminated, but a flag may be set at the controller. If theCPV then fails another diagnostic to determine whether the CPV isdegraded, then the MIL may be illuminated, notifying the driver of arequest to service the vehicle. However, a cleaning operation conductedon the CPV as discussed at FIG. 9 may result in the CPV being cleaned.Thus, in such a case, the initial flag may be removed, such that thenext time the CPV doesn't pass a diagnostic test, the MIL is notautomatically illuminated. Method 1000 may then end.

Returning to 1040, in response to the fuel system vacuum being greaterthan the predetermined threshold vacuum, method 1000 may proceed to1055. At 1055, method 1000 may include indicating that the CPV isdegraded. In other words, the CPV initially failed a diagnostic whichresulted in the CPV being cleaned, and then the CPV again failed thefollow-up diagnostic. Accordingly, indicating the CPV is degraded mayinclude illuminating a MIL at the vehicle dash, notifying the vehicleoperator of a request to service the vehicle. Furthermore, at 1055, theCVV may be commanded open.

Proceeding to 1050, method 1000 may include updating vehicle operatingparameters. For example, as the CPV was indicated to have not been ableto be successfully cleaned, the vehicle may be commanded to operate asfrequently as possible in an electric-only mode of operation, in orderto prevent engine manifold vacuum from being undesirably communicated tothe fuel system during engine operation until the issue has beenremedied. Method 1000 may then end.

Turning now to FIG. 11, an example timeline 1100 is depicted,illustrating a CPV cleaning operation, conducted in line with the methodof FIG. 9. Timeline 1100 includes plot 1105, indicating whetherconditions are met for purging of the canister (yes), or not (no), overtime. Timeline 1100 further includes plot 1110, indicating whether a CPVcleaning routine is requested (yes), or not (no), over time. Timeline1100 further includes plot 1115, indicating engine status (on or off),over time. It may be understood that in this example timeline, enginestatus being on refers to the engine combusting air and fuel. Timeline1100 further includes plot 1120, indicating engine intake manifoldvacuum, over time. Engine intake manifold vacuum may be either nearatmospheric pressure (atm), or negative (vac) with respect toatmospheric pressure, over time. Timeline 1100 further includes plot1125, indicating pressure pulsations or oscillations across the CPV,over time. The pressure oscillations are depicted as negative (−) ormore negative (−−−), as the engine manifold is applying a vacuum on thecanister, and the pressure oscillations are on top of the enginemanifold vacuum applied on the canister. While not shown at FIG. 11, thepressure oscillations may instead be depicted as in the inset 250 ofFIG. 2, without departing from the scope of this disclosure. Timeline1100 further includes plot 1130, indicating CPV status (open or closed),over time. Timeline 1100 further includes plot 1135, indicating CVVstatus (open or closed), over time. Timeline 1100 further includes plot1140, indicating canister load, over time. Canister load may increase(+) or decrease (−), over time.

In this example timeline 1100 it may be understood that a purging eventis in progress, and that a cleaning routine is requested to be conductedon the CPV. In other words, by time t0, the canister purging is alreadytaking place, and the canister is being purged according to method 900depicted at FIG. 9 such that a canister cleaning operation is to beconducted during the purging. Accordingly, at time t0, conditions aremet for canister purging (plot 1105), as the canister is in the processof being purged, and CPV cleaning is requested during the purge event(plot 1110). The engine is on, combusting air and fuel (pot 1115), anddue to the engine operation, there is a vacuum in the intake manifoldthat is being utilized to purge the canister. The CVV is open (plot1135), and the canister load is at a particular canister load at timet0. Furthermore, the frequency, phase, and amplitude of pressureoscillations across the CPV has been determined (plot 1125), and the CPVis being controlled accordingly (plot 1130), to time CPV opening andclosing events to coincide with low pressure differences across the CPVin terms of the pressure oscillations. Specifically, the stars 1127depict the instances where CPV opening/closing is timed with the lowpressure differences across the CPV in terms of the pressureoscillations. Thus, it may be seen from comparing plots 1125 and 1130that, between time t0 and t1, the CPV is timed to open and close attimes coinciding with low pressure differences across the CPV in termsof the pressure oscillations across the CPV.

At time t1, the cleaning routine commences. Accordingly, the CPV istransitioned from opening/closing at low pressure differences across theCPV, to opening/closing at high pressure differences across the CPV interms of the pressure oscillations across the CPV. By timing theopening/closing events to the high pressure differences in terms of thepressure oscillations across the CPV, whatever is preventing the CPVfrom properly sealing may be dislodged. As mentioned above with regardto FIG. 9, the cleaning routine where the CPV opening/closing events aretimed to coincide with high pressure differences in terms of thepressure oscillations across the CPV may last a predetermined duration,a predetermined number of opening/closing events, etc. In this exampletimeline, the CPV cleaning routine lasts from time t1 to time t2.

At time t2, after the cleaning routine has been conducted, theopening/closing events of the CPV are once again timed to coincide withlow pressure differences across the CPV in terms of pressureoscillations across the CPV. Controlling the CPV in this way proceedsafter time t2. It may be understood that timeline 1100 shows just aportion of the overall canister purging event, and thus, after time t2there may be one or more additional cleaning events where the CPV isonce again transitioned to being opened/closed at times coinciding withhigh pressure differences across the CPV in terms of the pressureoscillations. The purging operation may continue until the canister isclean, until conditions change such that the canister purging operationis aborted, etc. Furthermore, as timeline 1100 depicts a portion of theoverall canister purging operation, it may be understood that in theportion depicted, a ramping up of the purging of vapors is not depicted.However, it may be understood that a ramping up of the amount of fuelvapors routed to engine intake over time may occur during a purgingevent that also includes the CPV cleaning routine.

While example timeline 1100 depicts the CPV cleaning routine asconducted according to method 900 depicted at FIG. 9, subsequent to theconducting of such a routine it may be desirable to utilize method 1000depicted at FIG. 10 to assess whether the cleaning routine restored theability of the CPV to effectively seal off the engine intake from theevaporative emissions system and fuel system. Turning to FIG. 12, anexample timeline 1200 is shown, depicting a CPV test diagnostic routineto determine whether a CPV cleaning routine was successful, or not,according to the method of FIG. 10. Accordingly, timeline 1200 includesplot 1205, indicating whether conditions are met for conducting the CPVtest diagnostic (yes), or not (no), over time. Timeline 1200 furtherincludes plot 1210, indicating a status of the CPV (open or closed), andplot 1215, indicating a status of the CVV (open or closed), over time.Timeline 1200 further includes plot 1220, indicating pressure in thefuel system, over time. In this example timeline 1200, it may beunderstood that a pressure sensor (e.g. 126) positioned between the FTIVand the canister is utilized for monitoring pressure. In this way, thefuel system does not first have to be depressurized to conduct thediagnostic, thus reducing fuel vapors routed to the canister from thefuel tank. However, it may be understood that in other examples the fueltank may be coupled to the evaporative emissions system to conduct theCPV test diagnostic, without departing from the scope of this disclosure(for example in a case where the vehicle system does not include thepressure sensor between the FTIV and the canister). For plot 1220, fuelsystem pressure may be at atmospheric pressure, or negative (vacuum)with respect to atmospheric pressure. Timeline 1200 further includesplot 1225, indicating whether the CPV cleaning routine previouslyconducted was successful (yes) or not (no), over time. Until thediagnostic has been completed to determine whether the CPV isfunctioning as desired, it may not be applicable (n/a) as to whether thecleaning routine previously conducted was successful or not, as theresults have not yet been determined.

At time t0, conditions are not yet met for conducting the CPV test. Forexample, engine manifold vacuum may not be great enough for conductingthe CPV test. Accordingly, between time t0 and t1 the CPV is maintainedclosed, the CVV is maintained open, and pressure in the fuel system asmonitored by the pressure sensor (e.g. 126) remains near atmosphericpressure. Because the CPV test diagnostic has not yet been conducted, itis not applicable as yet whether the CPV cleaning routine wassuccessful.

At time t1, conditions are indicated to be met for conducting the CPVtest diagnostic. In this example timeline, it may be understood thatconditions have become met at time t1 because engine manifold vacuum hasbecome such that the diagnostic may be conducted. Accordingly, the CVVis commanded closed, and the CPV is maintained closed. Between time t1and t2, pressure does not develop in the fuel system to thepredetermined threshold vacuum, represented by dashed line 1221.Accordingly, it is indicated that the CPV cleaning routine wassuccessful (plot 1225), because the CPV no longer is indicated to becompromised in such a way that vacuum may be communicated from engineintake to the fuel system when the CPV is commanded closed. If thecleaning routine were not successful, then it may be understood that thepredetermined threshold vacuum (line 1221) would have been expected tohave been reached.

Responsive to the indication that the CPV cleaning routine wassuccessful, conditions are no longer indicated to be met for conductingthe CPV test diagnostic, and the CVV is returned to the open state.

The above description with regard to conducting cleaning operations wasdiscussed in terms of the CPV. To avoid redundant method figures and forbrevity, method figures and timelines are not depicted for conductingcleaning operations on a TPCV that has been determined to be degraded.However, it is herein recognized that a cleaning operation may beconducted in similar fashion as that of the CPV, without departing fromthe scope of this disclosure. For example, turning to FIG. 7 wheremethod 700 depicts steps for depressurization of a fuel tank by timingTPCV opening/closing events to coincide with low pressure differencesacross the TPCV, it may be understood that between steps 710 and 720,there may be another step (not shown), that includes a query as towhether TPCV cleaning is requested. If so, then method 700 may proceedto another method similar to that depicted at FIG. 9, where a TPCVcleaning routine may be conducted by transitioning (during the fuel tankdepressurization) to commanding open/closed the TPCV at times coincidingwith high pressure differences across the TPCV in terms of pressureoscillations across the TPCV. Instead of monitoring canister load (seestep 925 of method 900), fuel tank pressure may instead be monitored,such that the fuel tank depressurization may be concluded once fuel tankpressure has reached the predetermined threshold pressure (similar tostep 735 of method 700). In this way it may be understood that, during afuel tank depressurization routine, the fuel tank may be transitionedfrom timing the opening/closing of the TPCV to coincide with lowpressure differences in terms of pressure oscillations across the TPCV,to instead timing the opening/closing of the TPCV to coincide with highpressure differences in terms of pressure oscillations across the TPCV.In this way, the TPCV may be cleaned of any carbon buildup, debris,dust, etc., that may be preventing the TPCV from properly sealing.

Similar to that discussed above with regard to the CPV, after conductinga cleaning routine on the CPV, it may be ascertained as to whether theTPCV cleaning routine was successful, or not. Thus, another diagnostic,termed herein a TPCV test diagnostic, may be scheduled for after a TCPVcleaning routine has been conducted. Such a diagnostic may include, withthe engine combusting air and fuel, commanding open the CPV, andcommanding closed the FTIV and the TPCV, and monitoring vacuum build inthe sealed fuel tank. It may be understood that in order to conduct sucha diagnostic, the operational state of the FTIV may have to be known,such that it may be determined prior to conducting the TPCV diagnosticas to whether the FTIV is functioning as desired. If it is known thatthe FTIV is functioning as desired, then any vacuum build in the sealedfuel system may be attributed to the TPCV not sealing properly. In someexamples, rather than relying on engine manifold vacuum, a pumppositioned in the evaporative emissions system (for example a pumppositioned in the vent line that couples the canister to atmosphere) maybe used to generate the vacuum for conducting such a test. Clearly, sucha test further relies on the fuel system and evaporative emissionssystem being free from any sources of undesired evaporative emissions(aside from the potential degraded TPCV).

Still further, while not explicitly illustrated at FIG. 7, it is hereinrecognized that there may be opportunities to immediately command fullyopen the TPCV to depressurize the fuel tank, in similar fashion to thatdiscussed in terms of the CPV. More specifically, as discussed abovewith regard to FIGS. 3-4, remote engine start events and/or DFSO eventsmay allow for the CPV to be immediately commanded fully open (100% dutycycle), without concern of potential issues such as engine hesitationand/or stall. The same applies to the TPCV. For example, while notexplicitly illustrated at FIG. 7 it may be understood that in the eventof a remote start event where conditions are met for fuel tankdepressurization, or in the event of a DFSO event where conditions aremet for fuel tank depressurization, the TPCV may be immediatelycommanded to a 100% duty cycle to rapidly depressurize the fuel tank byrouting vapors to engine intake. One caveat is that a temperature of theemissions control device (e.g. 63) may have to be above its light-offtemperature. Thus, similar to that discussed in terms of the CPV, if thevehicle is in the process of depressurizing the fuel tank by timingopening/closing events to coincide with low pressure differences acrossthe TPCV in terms of pressure oscillations across the TPCV, and then aDFSO event is initiated, then the TPCV may be immediately commanded to100% duty cycle. In this way, opening/closing events of the TPCV may beminimized for a fuel tank depressurization.

Thus, the methods described herein may include determining a firstcondition that includes a request to purge the fuel vapor canister andin response thereto purging the canister by controlling frequency andphasing of CPV opening/closing events to correspond to instances wherepressure differences in terms of pressure oscillations across the CPVare lowest, and determining a second condition (which may not be thefirst condition) and in response thereto purging the canister at a 100%duty cycle without first purging at lower duty cycles. Many drive cyclesare expected to include both the first condition and the secondcondition, thus rendering it useful to select whether to purge thecanister by controlling frequency and phasing of CPV opening/closing tocorrespond to instances where pressure differences in terms of pressureoscillations across the CPV are lowest, or to purge the canister at a100% duty cycle. In some examples, the second condition may be initiatedduring the first condition, and in such a case, the CPV may betransitioned to stop being controlled to open and close when pressuredifferences in terms of pressure oscillations across the CPV are lowest,and to be instead immediately commanded to a 100% duty cycle which isnot dependent on the frequency, amplitude and phasing of the pressureoscillations. In still other examples, the first condition may beinitiated during the second condition, and in such a case, the CPV maybe transitioned to stop being controlled to a 100% duty cycle andinstead may be controlled as in the first condition where the frequencyand phasing of the CPV opening/closing events correspond to instanceswhere pressure differences in terms of pressure oscillations across theCPV are lowest, or purging may be discontinued. Instructions stored inmemory of the controller may include determining the first condition ascompared to the second condition, based on current vehicle operatingconditions and in response to information acquired at the controllerfrom various sensors. For example, the first condition may be indicatedin response to an indication that fueling and spark is being provided tothe engine, that the vehicle is occupied, and that a remote engine starthas not been initiated. Alternatively, the second condition may beindicated in response to an indication of a remote start event where thevehicle is unoccupied, or in response to an indication that fueling (andspark) has been discontinued to the engine while the vehicle is in theprocess of moving with the vehicle occupied.

In this way, a rate at which the CPV in a vehicle becomes degraded maybe reduced along with a reduction in NVH issues. Accordingly, customersatisfaction may be improved. Furthermore, by reducing CPV degradation,engine operation may be improved and engine lifetime may be increased.Additionally, when CPVs degrade, there are increased opportunity forundesired evaporative emissions to be released to the environment. Forexample, in a case where the CPV is degraded to a point where it doesnot fully close, during refueling events fuel vapors may be routedthrough the degraded CPV and may be released to atmosphere via the airintake system of the engine. In another example where the CPV isdegraded such that it does not open or sticks closed, the canister maynot be effectively cleaned in response to a request to purge thecanister of fuel vapors. Over time, inability to effectively clean thecanister may lead to bleed emissions from the canister as discussedabove.

The technical effect is to recognize that there are pressureoscillations across the CPV when there is an overall vacuum applied tothe CPV from the engine, and that if the CPV can be timed to open andclose in conjunction with points on the pressure oscillation wave thatcomprise the least or lowest pressure difference across the CPV, thendegradation of the CPV may be reduced. Said another way, the technicaleffect is to recognize that opening and closing the CPV when thepressure difference in terms of a pressure oscillation wave across theCPV during purging events is greatest may contribute greatly to CPVdegradation. Thus, by limiting the CPV opening and closing events towhen pressure across the CPV in terms of the pressure oscillation waveis lowest, such degradation may be greatly reduced.

A further technical effect is to recognize that there may be one or moreoptions for determining the frequency, amplitude and phasing of thepressure oscillations across the CPV. As discussed, one option includespredicting pressure oscillations from “first principles” based on dataretrieved from sensors of the vehicle related to engine speed, engineload, cam timing, ambient temperature, engine firing frequency,temperature of gas in the intake and purge line, etc. The controller mayacquire said data from the sensors and feed the data into a model whichpredicts the frequency, phasing and amplitude of pressure oscillationsacross the CPV. Additionally or alternatively, a purge line pressuresensor positioned between the CPV and engine intake may be used to inferpressure oscillations across the CPV. In some examples, the purge linepressure sensor may be used for feedback control means in addition tothe modeled pressure oscillations, to ensure proper phasing of thepressure oscillations. The timing of opening and closing of the CPVduring purging events may thus in some examples be correlated with dataretrieved from the purge line pressure sensor related to when pressureacross the CPV is lowest in terms of the pressure oscillations acrossthe CPV. In yet another example, a technical effect is to recognizethat, additionally or alternatively, existing pressure sensors in theintake (e.g. MAP sensor) and fuel system (FTIV) may be used to inferpressure oscillations across the CPV.

A further technical effect is to recognize that for hybrid vehicles withlimited engine run time, effectively purging the canister may bechallenging, and thus it is desirable to find opportunities toaggressively purge the canister while also avoiding issues related toopening/closing the CPV when pressure differences across the CPV interms of pressure oscillations are greatest. Thus, a technical effect isto recognize that there may be certain vehicle operating conditionswhere the CPV may be immediately commanded to a 100% duty cycle, whichserves the purpose of drastically reducing opportunity foropening/closing the CPV when pressure across the CPV in terms ofpressure oscillations is greatest, while also aggressively purging thecanister. Those conditions may include but may not be limited to remoteengine start events, and when the vehicle is operated in DFSO mode. Byusing the methodology described herein to time CPV opening and closingevents to be concurrent with (e.g. within a predetermined time of peaklowest pressure difference) the lowest pressure difference across theCPV in terms of the pressure oscillation wave when the vehicle is not inDFSO mode or in the process of a remote start, and to command the CPV to100% duty cycle when the vehicle is in DFSO mode or in the process of aremote start, CPV degradation may be reduced and canister purgingefficiency may be increased. In turn, customer satisfaction may beimproved, engine lifetime may be increased, and release of undesiredevaporative emissions to atmosphere may be reduced.

Thus, the systems and methods discussed herein may enable one or moresystems and one or more methods. In one example, a method comprisespurging a fuel vapor canister that captures and stores fuel vapors froma fuel system of a vehicle by synchronizing a timing of opening andclosing events of a canister purge valve to correspond with instanceswhere a pressure difference across the canister purge valve is lower ascompared to higher in terms of pressure oscillations across the canisterpurge valve during purging the fuel vapor canister. In a first exampleof the method, the method further comprises adjusting the timing of theopening and the closing events of the canister purge valve in responseto changes in the pressure oscillations across the canister purge valveduring purging the fuel vapor canister. A second example of the methodoptionally includes the first example, and further comprises controllinga duty cycle of the canister purge valve while synchronizing the timingof the opening and the closing events of the canister purge valve tocorrespond with the instances where the pressure difference across thecanister purge valve is lower as compared to higher in terms of thepressure oscillations. A third example of the method optionally includesany one or more or each of the first through second examples, andfurther includes wherein the pressure oscillations are a function of atleast operating conditions of an engine that receives purge gasses fromthe fuel vapor canister and further comprising: determining a frequency,a phase, and an amplitude of the pressure oscillations across thecanister purge valve in order to synchronize the timing of the openingand the closing events of the canister purge valve to correspond withthe instances where the pressure difference across the canister purgevalve are lower as compared to higher in terms of the pressureoscillations. A fourth example of the method optionally includes any oneor more or each of the first through third examples, and furtherincludes wherein determining the frequency, the phase and the amplitudeof the pressure oscillations includes mapping the pressure oscillationsbased on one or more of at least an engine speed, an engine load, atiming of opening and/or closing of intake and/or exhaust valves of theengine, and an ambient temperature. A fifth example of the methodoptionally includes any one or more or each of the first through fourthexamples, and further includes wherein determining the frequency, thephase and the amplitude of the pressure oscillations is based at leastin part on feedback from a pressure sensor at the canister purge valve.A sixth example of the method optionally includes any one or more oreach of the first through fifth examples, and further includes whereindetermining the frequency, the phase, and the amplitude of the pressureoscillations is based at least in part on a difference between an engineintake pressure and a fuel system pressure with the fuel system coupledto atmosphere, corrected for an offset that is modelled as a function ofa restriction of a buffer section of the fuel vapor canister. A seventhexample of the method optionally includes any one or more or each of thefirst through sixth examples, and further includes wherein synchronizingthe timing of the opening and the closing events of the canister purgevalve to correspond with the instances where the pressure differenceacross the canister purge valve is lower as compared to higher in termsof the pressure oscillations across the canister purge valve furthercomprises controlling a pulse width modulation signal to the canisterpurge valve based on the pressure oscillations across the canister purgevalve. An eighth example of the method optionally includes any one ormore or each of the first through seventh examples, and further includeswherein synchronizing the timing of the opening and the closing eventsof the canister purge valve to correspond with the instances where thepressure difference across the canister purge valve is lower as comparedto higher in terms of the pressure oscillations across the canisterpurge valve improves durability and reduces issues related to noise,vibration and harshness of the canister purge valve. A ninth example ofthe method optionally includes any one or more or each of the firstthrough eighth examples, and further includes wherein synchronizing thetiming of the opening and the closing events of the canister purge valveto correspond with the instances where the pressure difference acrossthe canister purge valve is lower as compared to higher in terms of thepressure oscillations across the canister purge valve further comprisescontrolling the canister purge valve to open and/or close within athreshold time duration in relation to the pressure oscillations acrossthe canister purge valve, the threshold time duration corresponding towhen the pressure difference is lower as compared to higher in terms ofthe pressure oscillations across the canister purge valve.

Another example of a method for a vehicle comprises reducing degradationand issues related to noise, vibration and harshness of a canister purgevalve by timing opening and closing events of the canister purge valveto coincide with when a pressure difference across the canister purgevalve is lower than a threshold pressure difference in terms of pressureoscillations across the canister purge valve while purging a fuel vaporcanister of fuel vapors. In a first example of the method, the methodfurther includes wherein the threshold pressure difference is determinedas a function of the pressure oscillations across the canister purgevalve; and wherein the threshold pressure difference is updated as thepressure oscillations change during the course of purging the fuel vaporcanister of fuel vapors. A second example of the method optionallyincludes the first example, and further comprises determining afrequency, a phase and an amplitude of the pressure oscillations acrossthe canister purge valve and controlling a pulse width modulation signalto the canister purge valve in order to synchronize the timing of theopening and the closing of the canister purge valve to coincide withwhen the pressure difference across the canister purge valve is lowerthan the threshold pressure difference in terms of the pressureoscillations across the canister purge valve. A third example of themethod optionally includes any one or more or each of the first throughsecond examples, and further includes wherein reducing degradation andissues related to noise, vibration and harshness of the canister purgevalve further comprises: commanding the canister purge valve fully openwithout first commanding lower percentage duty cycles in response to arequest for purging the fuel vapor canister, under select vehicleoperating conditions. A fourth example of the method optionally includesany one or more or each of the first through third examples, and furtherincludes wherein the select vehicle operating conditions includes aremote start event of an engine of the vehicle, where the vehicle isindicated to be unoccupied and where an exhaust catalyst is at or abovean operating temperature of the exhaust catalyst. A fifth example of themethod optionally includes any one or more or each of the first throughfourth examples, and further includes wherein the select vehicleoperating conditions includes a deceleration fuel shut-off event wherefueling to an engine of the vehicle is shut off but where intake andexhaust valves of the engine continue to open and close, and where anexhaust catalyst is at or above an operating temperature of the exhaustcatalyst.

An example of a system for a vehicle comprises a canister purge valvepositioned in a purge line fluidically coupling a fuel vapor canister toan intake of an engine; and a controller with computer readableinstructions stored on non-transitory memory that when executed, causethe controller to: receive a request to purge the fuel vapor canister offuel vapors to the engine; in a first condition, control the canisterpurge valve in a first mode to synchronize a timing of opening andclosing of the canister purge valve as a function of pressureoscillations across the canister purge valve; and in a second condition,control the canister purge valve in a second mode that includescommanding the canister purge valve fully open without first commandinglower percentage duty cycles in response to the request for purging thefuel vapor canister. In a first example of the system, the systemfurther comprises an exhaust catalyst positioned in an exhaust of theengine; and wherein the controller stores further instructions tocontrol the canister purge valve in the first mode or the second modeprovided that a temperature of the exhaust catalyst is at or above athreshold temperature. A second example of the system optionallyincludes the first example, and further comprises one or more of seatload cells, door sensing technology and/or onboard cameras forindicating occupancy of the vehicle; fuel injectors for fueling theengine; and wherein the controller stores further instructions tocontrol the canister purge valve in the second mode in response to anindication of a remote start of the engine where the vehicle is furtherindicated to be unoccupied, or in response to an indication of adeceleration fuel shut off event where fuel to the engine isdiscontinued while engine intake and engine exhaust valves continue tooperate. A third example of the system optionally includes any one ormore or each of the first through second examples, and further comprisesa crankshaft position sensor; a mass air flow sensor positioned in theintake of the engine; a throttle positioned in the intake of the engine;an ambient air temperature sensor; position sensors for engine intakeand exhaust valves; an intake temperature sensor; a manifold airpressure sensor positioned in the intake; a fuel tank temperature sensorpositioned in a fuel system; wherein the controller stores furtherinstructions to map a frequency, a phase and an amplitude of thepressure oscillations across the canister purge valve based on dataretrieved from a plurality of two or more of the crankshaft positionsensor, the mass air flow sensor, the ambient air temperature sensor,the position sensors for the engine intake and exhaust valves, theintake temperature sensor, the manifold air pressure sensor and/or thefuel tank temperature sensor; and wherein controlling the canister purgevalve in the first mode to synchronize the timing of opening and closingof the canister purge valve as a function of pressure oscillationsacross the canister purge valve includes controlling a pulse widthmodulation signal to the canister purge valve as a function of thefrequency, the phase and the amplitude of the pressure oscillations,such that opening and closing events of the canister purge valve occurat times in terms of the pressure oscillations where a pressuredifference across the canister purge valve is less than a thresholdpressure difference, where the threshold pressure difference is set as afunction of the frequency, the phase and the amplitude of the pressureoscillations.

Note that the example control and estimation routines included hereincan be used with various engine and/or vehicle system configurations.The control methods and routines disclosed herein may be stored asexecutable instructions in non-transitory memory and may be carried outby the control system including the controller in combination with thevarious sensors, actuators, and other engine hardware. The specificroutines described herein may represent one or more of any number ofprocessing strategies such as event-driven, interrupt-driven,multi-tasking, multi-threading, and the like. As such, various actions,operations, and/or functions illustrated may be performed in thesequence illustrated, in parallel, or in some cases omitted. Likewise,the order of processing is not necessarily required to achieve thefeatures and advantages of the example embodiments described herein, butis provided for ease of illustration and description. One or more of theillustrated actions, operations and/or functions may be repeatedlyperformed depending on the particular strategy being used. Further, thedescribed actions, operations and/or functions may graphically representcode to be programmed into non-transitory memory of the computerreadable storage medium in the engine control system, where thedescribed actions are carried out by executing the instructions in asystem including the various engine hardware components in combinationwith the electronic controller.

It will be appreciated that the configurations and routines disclosedherein are exemplary in nature, and that these specific embodiments arenot to be considered in a limiting sense, because numerous variationsare possible. For example, the above technology can be applied to V-6,I-4, I-6, V-12, opposed 4, and other engine types. The subject matter ofthe present disclosure includes all novel and non-obvious combinationsand sub-combinations of the various systems and configurations, andother features, functions, and/or properties disclosed herein.

As used herein, the term “approximately” is construed to mean plus orminus five percent of the range unless otherwise specified.

The following claims particularly point out certain combinations andsub-combinations regarded as novel and non-obvious. These claims mayrefer to “an” element or “a first” element or the equivalent thereof.Such claims should be understood to include incorporation of one or moresuch elements, neither requiring nor excluding two or more suchelements. Other combinations and sub-combinations of the disclosedfeatures, functions, elements, and/or properties may be claimed throughamendment of the present claims or through presentation of new claims inthis or a related application. Such claims, whether broader, narrower,equal, or different in scope to the original claims, also are regardedas included within the subject matter of the present disclosure.

The invention claimed is:
 1. A method comprising: purging a fuel vaporcanister that captures and stores fuel vapors from a fuel system of avehicle by synchronizing a timing of opening and closing events of acanister purge valve to correspond with instances where a pressuredifference across the canister purge valve is lower as compared tohigher in terms of pressure oscillations across the canister purge valveduring purging the fuel vapor canister.
 2. The method of claim 1,further comprising adjusting the timing of the opening and the closingevents of the canister purge valve in response to changes in thepressure oscillations across the canister purge valve during purging thefuel vapor canister.
 3. The method of claim 1, further comprisingcontrolling a duty cycle of the canister purge valve while synchronizingthe timing of the opening and the closing events of the canister purgevalve to correspond with the instances where the pressure differenceacross the canister purge valve is lower as compared to higher in termsof the pressure oscillations.
 4. The method of claim 1, wherein thepressure oscillations are a function of at least operating conditions ofan engine that receives purge gasses from the fuel vapor canister andfurther comprising: determining a frequency, a phase, and an amplitudeof the pressure oscillations across the canister purge valve in order tosynchronize the timing of the opening and the closing events of thecanister purge valve to correspond with the instances where the pressuredifference across the canister purge valve are lower as compared tohigher in terms of the pressure oscillations.
 5. The method of claim 4,wherein determining the frequency, the phase and the amplitude of thepressure oscillations includes mapping the pressure oscillations basedon one or more of at least an engine speed, an engine load, a timing ofopening and/or closing of intake and/or exhaust valves of the engine,and an ambient temperature.
 6. The method of claim 4, whereindetermining the frequency, the phase and the amplitude of the pressureoscillations is based at least in part on feedback from a pressuresensor at the canister purge valve.
 7. The method of claim 4, whereindetermining the frequency, the phase, and the amplitude of the pressureoscillations is based at least in part on a difference between an engineintake pressure and a fuel system pressure with the fuel system coupledto atmosphere, corrected for an offset that is modelled as a function ofa restriction of a buffer section of the fuel vapor canister.
 8. Themethod of claim 1, wherein synchronizing the timing of the opening andthe closing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillationsacross the canister purge valve further comprises controlling a pulsewidth modulation signal to the canister purge valve based on thepressure oscillations across the canister purge valve.
 9. The method ofclaim 1, wherein synchronizing the timing of the opening and the closingevents of the canister purge valve to correspond with the instanceswhere the pressure difference across the canister purge valve is loweras compared to higher in terms of the pressure oscillations across thecanister purge valve improves durability and reduces issues related tonoise, vibration and harshness of the canister purge valve.
 10. Themethod of claim 1, wherein synchronizing the timing of the opening andthe closing events of the canister purge valve to correspond with theinstances where the pressure difference across the canister purge valveis lower as compared to higher in terms of the pressure oscillationsacross the canister purge valve further comprises controlling thecanister purge valve to open and/or close within a threshold timeduration in relation to the pressure oscillations across the canisterpurge valve, the threshold time duration corresponding to when thepressure difference is lower as compared to higher in terms of thepressure oscillations across the canister purge valve.
 11. A method fora vehicle comprising: reducing degradation and issues related to noise,vibration and harshness of a canister purge valve by timing opening andclosing events of the canister purge valve to coincide with when apressure difference across the canister purge valve is lower than athreshold pressure difference in terms of pressure oscillations acrossthe canister purge valve while purging a fuel vapor canister of fuelvapors.
 12. The method of claim 11, wherein the threshold pressuredifference is determined as a function of the pressure oscillationsacross the canister purge valve; and wherein the threshold pressuredifference is updated as the pressure oscillations change during thecourse of purging the fuel vapor canister of fuel vapors.
 13. The methodof claim 12, further comprising determining a frequency, a phase and anamplitude of the pressure oscillations across the canister purge valveand controlling a pulse width modulation signal to the canister purgevalve in order to synchronize the timing of the opening and the closingof the canister purge valve to coincide with when the pressuredifference across the canister purge valve is lower than the thresholdpressure difference in terms of the pressure oscillations across thecanister purge valve.
 14. The method of claim 11, wherein reducingdegradation and issues related to noise, vibration and harshness of thecanister purge valve further comprises: commanding the canister purgevalve fully open without first commanding lower percentage duty cyclesin response to a request for purging the fuel vapor canister, underselect vehicle operating conditions.
 15. The method of claim 14, whereinthe select vehicle operating conditions includes a remote start event ofan engine of the vehicle, where the vehicle is indicated to beunoccupied and where an exhaust catalyst is at or above an operatingtemperature of the exhaust catalyst.
 16. The method of claim 14, whereinthe select vehicle operating conditions includes a deceleration fuelshut-off event where fueling to an engine of the vehicle is shut off butwhere intake and exhaust valves of the engine continue to open andclose, and where an exhaust catalyst is at or above an operatingtemperature of the exhaust catalyst.
 17. A system for a vehicle,comprising: a canister purge valve positioned in a purge linefluidically coupling a fuel vapor canister to an intake of an engine;and a controller with computer readable instructions stored onnon-transitory memory that when executed, cause the controller to:receive a request to purge the fuel vapor canister of fuel vapors to theengine; in a first condition, control the canister purge valve in afirst mode to synchronize a timing of opening and closing of thecanister purge valve as a function of pressure oscillations across thecanister purge valve; and in a second condition, control the canisterpurge valve in a second mode that includes commanding the canister purgevalve fully open without first commanding lower percentage duty cyclesin response to the request for purging the fuel vapor canister.
 18. Thesystem of claim 17, further comprising an exhaust catalyst positioned inan exhaust of the engine; and wherein the controller stores furtherinstructions to control the canister purge valve in the first mode orthe second mode provided that a temperature of the exhaust catalyst isat or above a threshold temperature.
 19. The system of claim 17, furthercomprising one or more of seat load cells, door sensing technologyand/or onboard cameras for indicating occupancy of the vehicle; fuelinjectors for fueling the engine; and wherein the controller storesfurther instructions to control the canister purge valve in the secondmode in response to an indication of a remote start of the engine wherethe vehicle is further indicated to be unoccupied, or in response to anindication of a deceleration fuel shut off event where fuel to theengine is discontinued while engine intake and engine exhaust valvescontinue to operate.
 20. The system of claim 17, further comprising: acrankshaft position sensor; a mass air flow sensor positioned in theintake of the engine; a throttle positioned in the intake of the engine;an ambient air temperature sensor; position sensors for engine intakeand exhaust valves; an intake temperature sensor; a manifold airpressure sensor positioned in the intake; a fuel tank temperature sensorpositioned in a fuel system; wherein the controller stores furtherinstructions to map a frequency, a phase and an amplitude of thepressure oscillations across the canister purge valve based on dataretrieved from a plurality of two or more of the crankshaft positionsensor, the mass air flow sensor, the ambient air temperature sensor,the position sensors for the engine intake and exhaust valves, theintake temperature sensor, the manifold air pressure sensor and/or thefuel tank temperature sensor; and wherein controlling the canister purgevalve in the first mode to synchronize the timing of opening and closingof the canister purge valve as a function of pressure oscillationsacross the canister purge valve includes controlling a pulse widthmodulation signal to the canister purge valve as a function of thefrequency, the phase and the amplitude of the pressure oscillations,such that opening and closing events of the canister purge valve occurat times in terms of the pressure oscillations where a pressuredifference across the canister purge valve is less than a thresholdpressure difference, where the threshold pressure difference is set as afunction of the frequency, the phase and the amplitude of the pressureoscillations.